DIFFERENTIAL LIFE HISTORY PHASE EXPRESSION IN TWO COEXISTING SPECIES OF SCYTOSIPHON (PHAEOPHYCEAE) IN NORTHERN CHILE1

The identity of two phaeophycean taxa that monopolized the middle‐lower rocky intertidal zone of a coastal area chronically exposed to copper mine wastes in northern Chile was unraveled. One of them was preliminarily identified as the gametophytic stage of Scytosiphon lomentaria (Lyngbye) Link. The other, a dark crust, resembled the alternate stage of some Scytosiphon species. Comparative analysis of morphology, life history, and DNA sequences strongly suggests that crusts corresponded to sporophytic S. tenellus Kogame and confirm that erect thalli belonged to S. lomentaria. A clear segregation of erect and crustose thalli was found using internal transcribed spacer region 1 and RUBISCO spacer sequences. Furthermore, whereas crusts always grouped with S. tenellus, erect thalli always grouped with S. lomentaria. Life history studies failed to connect the two entities. First, field‐collected S. tenellus produced progeny that either recycled the crust, which reproduced by unilocular zoidangia, or developed into erect thalli. The latter, unlike typical gametophytic S. lomentaria, developed patchy sori of plurilocular zoidangia. Second, S. lomentaria displayed a direct‐type life cycle, in which progeny from erect individuals only developed into erect thalli and produced only plurilocular zoidangia. This constitutes the first experimental study on Scytosiphon from the Pacific coast of South America and the first report of S. tenellus on this coast. It is also the first report of the crustose stage of Scytosiphon appearing as a perennial and dominant algal species in a temperate rocky intertidal system.     

Molecular and morphologically distinct Scytosiphon species (Scytosiphonales,Phaeophyceae) display similar antioxidant capacities1

The taxonomic status of an alga with complanate thalli, occurring in central Chile and belonging to the genus Scytosiphon, was elucidated. Morphological and molecular features demonstrated that, in addition to the known and widespread constricted S. lomentaria (Lyngb.) Link that occurs along the Chilean coast, there is a Scytosiphon with complanate thalli that occurs only in central Chile—S. gracilis Kogame. Morphological analyses of this previously unreported complanate Scytosiphon showed thalli without constrictions, coherent plurilocular sporangia without ascocysts, and phaeophycean hairs arising from cortical cells. Furthermore, sequences of the internal transcribed spacer (ITS1 and ITS2) regions of the complanate Scytosiphon were 99.8% and 100% identical to those detected in S. gracilis from Korea. ITS‐based comparative analyses showed that complanate Scytosiphon grouped in a different clade than S. lomentaria and S. tenellus Kogame from various parts of the world, including Chilean species. Moreover, molecular analyses suggest the occurrence of two distinct ITS types of S. lomentaria in northern Chile, corresponding to the Korean and Greek types. On the other hand, biochemical analyses of copper‐induced antioxidant responses in S. gracilis and S. lomentaria showed an identical increase in antioxidant enzyme activities. These results suggest that copper tolerance might be a constitutive trait in these species of Scytosiphon.     

Temperature requirements ofScytosiphon lomentaria (Scytosiphonales,Phaeophyta) from the Gulf of Thessaloniki,Greece, in relation to geographic distribution

Temperature requirements for growth, reproduction and formation of macrothalli of a day-neutral strain ofScytosiphon lomentaria from the Gulf of Thessaloniki were experimentally determined and correlated with the geographic distribution in the North Atlantic Ocean. The microthallus grew in a wider temperature interval and better at higher temperatures than did the macrothallus. Germlings acclimated to 5 or 15°C grew sufficiently (>20% of maximum rate) and developed into macrothalli at 5–25°C and 5–27°C. Macrothalli acclimated to 10 or 15°C grew sufficiently at 5–20°C. Macrothalli acclimated to 15°C survived at −1°C and reproduced at 5 to 23°C. Regardless of the acclimation temperature, germlings and macrothalli grew optimally (>80% of maximum rate) at 15–25°C and at 10–15°C. The experimental data explain only the southern distribution boundary ofScytosiphon in the North Atlantic. This boundary is composite in nature: on the European coasts it is a growth boundary, whereas on the American coasts it is a lethal one.     

Phylogeography of Plathymenia reticulata (Leguminosae) reveals patterns of recent range expansion towards northeastern Brazil and southern Cerrados in Eastern Tropical South America

Little is known about past vegetation dynamics in Eastern Tropical South America (ETSA). Here we describe patterns of chloroplast (cp) DNA variation in Plathymenia reticulata, a widespread tree in the ETSA Atlantic Forest and Cerrado biomes, but not found in the xeromorphic Caatinga. Forty one populations, comprising 220 individuals, were analysed by sequencing the trnS‐trnG and trnL‐trnL‐trnF cpDNA regions. Combined, they resulted in 18 geographically structured haplotypes. The central region of the sampling area, comprising Minas Gerais and Goiás Brazilian states, is a centre of genetic diversity and probably the most longstanding area of the distribution range of the species. In contrast, populations from northeastern Brazil and the southern Cerrados showed very low diversity levels, almost exclusively with common haplotypes which are also found in the central region. Coupled with a long‐branched star‐like network, these patterns suggest a recent range expansion of P. reticulata to those regions from central region sources. The recent origin of the species (in the early Pleistocene) or the extinction of some populations due to drier and cooler climate during the last glacial maximum could have been responsible for that phylogeographic pattern. The populations from northeastern Brazil originated from two colonization routes, one eastern (Atlantic) and one western (inland). Due to its high diversity and complex landscape, the central region, especially central‐north Minas Gerais (between 15°–18° S and 42°–46° W), should be given the highest priority for conservation.     

Morphological Differentiation Between Geographically Separated Populations of <Emphasis Type="Italic">Neomysis integer</Emphasis> and <Emphasis Type="Italic">Mesopodopsis slabberi</Emphasis> (Crustacea,Mysida)

Morphological variation was examined in Neomysis integer and Mesopodopsis slabberi, two abundant, low dispersal mysid species (Crustacea, Mysida) along the European coasts. Both species dominate the hyperbenthic communities in the northeast Atlantic, and M. slabberi is also widely distributed in the Mediterranean and Black Sea. Three populations of these species were sampled throughout their distribution range; samples of N. integer were collected in the northeast Atlantic Eems-Dollard, Gironde and Guadalquivir estuaries; in the case of M. slabberi, mysids were sampled in two northeast Atlantic estuaries (Eems-Dollard and Guadalquivir) and one Mediterranean site (Ebro Delta). A total of 12 morphometric and 2 meristic characters were measured from 30–64 mysids per sample. Multivariate analysis showed clear morphometric differences between populations of both species. The morphological differentiation within M. slabberi was highly concordant with the available genetic data from mitochondrial loci, pointing to a large divergence between the Atlantic and Mediterranean populations. However, due to some overlap of individuals between the different populations, the present morphometric analysis does not suffice to assign the different populations to a separate (sub)species status. In the case of N. integer, the morphometric patterns showed a divergence of the Gironde population. Differentiation of populations within this mysid, as in M. slabberi, were mainly related to eye and telson morphology. Potential interactions of the mysid morphology and environmental conditions are discussed.     

Characterization of microsatellite markers for snouted treefrogs in the Scinax perpusillus species group (Anura, Hylidae)

We characterized eight microsatellite loci for snouted treefrogs in the Scinax perpusillus species group, a group of hylid frogs endemic to the Atlantic Coastal Forest of Brazil, and tested their utility in mainland and island species of the complex. All eight loci were polymorphic in one population of S. perpusillus; four of the loci showed excess homozygosity and three of those deviated from Hardy–Weinberg expectations, possibly due to null alleles, inbreeding, or population structure in sampled individuals. Six loci amplified and were polymorphic in S. arduous, S. argyreornatus, and S. faivovichi, but only one in S. alcatraz. These markers will be useful for quantifying effects of habitat fragmentation on population genetic diversity and connectivity in coastal and island populations of this threatened species group.     

Trans‐Pacific and trans‐Arctic pathways of the intertidal macroalga Fucus distichus L. reveal multiple glacial refugia and colonizations from the North Pacific to the North Atlantic

Aim We examined the phylogeography of the cold‐temperate macroalgal species Fucus distichus L., a key foundation species in rocky intertidal shores and the only Fucus species to occur naturally in both the North Pacific and the North Atlantic. Location North Pacific and North Atlantic oceans (42° to 77° N). Methods We genotyped individuals from 23 populations for a mitochondrial DNA (mtDNA) intergenic spacer (IGS) (n = 608) and the cytochrome c oxidase subunit I (COI) region (n = 276), as well as for six nuclear microsatellite loci (n = 592). Phylogeographic structure and connectivity were assessed using population genetic and phylogenetic network analyses. Results IGS mtDNA haplotype diversity was highest in the North Pacific, and divergence between Pacific haplotypes was much older than that of the single cluster of Atlantic haplotypes. Two ancestral Pacific IGS/COI clusters led to a widespread Atlantic cluster. High mtDNA and microsatellite diversities were observed in Prince William Sound, Alaska, 11 years after severe disturbance by the 1989 Exxon Valdez oil spill. Main conclusions At least two colonizations occurred from the older North Pacific populations to the North Atlantic between the opening of the Bering Strait and the onset of the Last Glacial Maximum. One colonization event was from the Japanese Archipelago/eastern Aleutians, and a second was from the Alaskan mainland around the Gulf of Alaska. Japanese populations probably arose from a single recolonization event from the eastern Aleutian Islands before the North Pacific–North Atlantic colonization. In the North Atlantic, the Last Glacial Maximum forced the species into at least two known glacial refugia: the Nova Scotia/Newfoundland (Canada) region and Andøya (northern Norway). The presence of two private haplotypes in the central Atlantic suggests the possibility of colonization from other refugia that are now too warm to support F. distichus. With the continuing decline in Arctic ice cover as a result of global climate change, renewed contact between North Pacific and North Atlantic populations of Fucus species is expected.     

The geographic scale of speciation in a marine snail with high dispersal potential

Aim We use the Stramonita haemastoma species complex (Muricidae) to investigate the geographic scale of speciation in a marine snail with a long pelagic larval duration (PLD) of 2–3 months and, consequently, high dispersal potential. We aim to: (1) delimit species within Stramonita, (2) discover the phylogenetic relationship among them, (3) map their distributions, and (4) infer the age and likely cause of speciation events. Location Tropical intertidal of the Atlantic and eastern Pacific Oceans. Methods We use one nuclear and two mitochondrial genes to construct a molecular phylogeny of the S. haemastoma species complex. We first test the monophyly of the genus and of the species complex, and then use statistical methods to delimit species within the complex. We incorporate information from museum collections and the literature to map distributions and to look for diagnostic morphological traits. We use fossils to date our phylogeny. Results The genus Stramonita is monophyletic and restricted to the tropical and warm‐temperate Atlantic and eastern Pacific oceans. The genus is composed of Stramonita delessertiana and six members of the S. haemastoma complex: S. haemastoma, Stramonita rustica, Stramonita floridana, Stramonita canaliculata, Stramonita biserialis and Stramonita brasiliensis (new species described herein). These species are supported by reciprocal monophyly in mitochondrial gene trees, together with independent evidence from morphology, distribution and the nuclear gene. The species are almost entirely allopatric, with only three instances of sympatry. Two species have unusually wide distributions, consistent with their long PLD; one of these is amphi‐Atlantic. Main conclusions Despite the long PLD of Stramonita, speciation has occurred within the Atlantic, both in response to barriers operating at the largest geographical scale (the width of Atlantic, but not the Amazon barrier) and at a smaller scale within the western Atlantic.     

Phylogeography of an estuarine mysid, Neomysis integer (Crustacea, Mysida), along the north-east Atlantic coasts

Aim The brackish water mysid, Neomysis integer, is one of the most common mysid species along the coasts of the north‐east Atlantic. In the present study, the phylogeographical patterns were examined throughout the distribution range of N. integer. In particular, the latitudinal trends in genetic diversity and the distribution of genetic variation were examined in order to elucidate the imprints of the Pleistocene glaciations. Location North‐east Atlantic coasts from the Baltic Sea to the south of Spain. Methods A total of 461 specimens from 11 populations were analysed by means of single‐stranded conformation polymorphism analysis combined with DNA sequencing of a fragment of the mitochondrial cytochrome c oxidase I gene. The genetic structure was examined by using a progression of phylogenetic, demographic and population genetic analyses to elucidate not only the geographical structure, but also the evolutionary history producing that structure. Results The levels of genetic diversity were relatively uniform throughout the distribution range, with the exception of a decline at the northern and southern edges of distribution. A high heterogeneity was observed between the populations analysed (global Φ_ST = 0.787). This is caused by the disparate distribution of the cytochrome oxidase I haplotypes, with several population‐specific haplotypes. A clear genetic break (2.4% sequence divergence) occurred between the southernmost Guadalquivir population and all other populations. Main conclusions The present study corroborates the expectations of the genetic patterns typically observed in an estuarine species. The within‐population variability was low, whereas a significant (moderate to high) divergence was observed between populations. Phylogeographical analysis revealed that northern populations within the English Channel, North Sea and Baltic Sea are characterized by several widespread haplotypes, while the Irish population and all sites south of the Bay of Biscay consist solely of unique haplotypes. This pattern, combined with the relative high levels of genetic diversity, could be indicative for the presence of a glacial refugium in the English Channel region. Under this scenario N. integer must have survived the Last Glacial Maximum in the palaeoriver system present in that region.     

Multiple transisthmian divergences,extensive cryptic diversity,occasional long‐distance dispersal,and biogeographic patterns in a marine coastal isopod with an amphi‐American distribution

Excirolana braziliensis is a coastal intertidal isopod with a broad distribution spanning the Atlantic and Pacific tropical and temperate coasts of the American continent. Two separate regional studies (one in Panama and one in Chile) revealed the presence of highly genetically divergent lineages, implying that this taxon constitutes a cryptic species complex. The relationships among the lineages found in these two different regions and in the rest of the distribution, however, remain unknown. To better understand the phylogeographic patterns of E. braziliensis, we conducted phylogenetic analyses of specimens from much of its entire range. We obtained DNA sequences for fragments of four mitochondrial genes (16S rDNA, 12S rDNA, COI, and Cytb) and also used publicly available sequences. We conducted maximum likelihood and Bayesian phylogenetic reconstruction methods. Phylogeographic patterns revealed the following: (1) new highly divergent lineages of E. braziliensis; (2) three instances of Atlantic–Pacific divergences, some of which appear to predate the closure of the Isthmus of Panama; (3) the distributional limit of highly divergent lineages found in Brazil coincides with the boundary between two major marine coastal provinces; (4) evidence of recent long‐distance dispersal in the Caribbean; and (5) populations in the Gulf of California have closer affinities with lineages further south in the Pacific, which contrasts with the closer affinity with the Caribbean reported for other intertidal organisms. The high levels of cryptic diversity detected also bring about challenges for the conservation of this isopod and its fragile environment, the sandy shores. Our findings underscore the importance of comprehensive geographic sampling for phylogeographic and taxonomical studies of broadly distributed putative species harboring extensive cryptic diversity.     

Mosquitoes in degraded and preserved areas of the Atlantic Forest and potential for vector‐borne disease risk in the municipality of São Paulo,Brazil

In order to assess the epidemiological potential of the Culicidae species in remaining areas of the Brazilian Atlantic Forest, specimens of this family were collected in wild and anthropic environments. A total of 9,403 adult mosquitoes was collected from May, 2009 to June, 2010. The most prevalent among species collected in the wild environment were Anopheles (Kerteszia) cruzii, the Melanoconion section of Culex (Melanoconion), and Aedes serratus, while the most common in the anthropic site were Coquillettidia chrysonotum/albifera, Culex (Culex) Coronator group, and An. (Ker.) cruzii. Mosquito richness was similar between environments, although the abundance of individuals from different species varied. When comparing diversity patterns between environments, anthropic sites exhibited higher richness and evenness, suggesting that environmental stress increased the number of favorable niches for culicids, promoting diversity. Increased abundance of opportunistic species in the anthropic environment enhances contact with culicids that transmit vector‐borne diseases.     

The distribution of benthic marine algae in relation to the temperature regulation of their life histories

Mainly on the basis of the distribution patterns of 42 species of the recently revised genus Cladopkora (Chlorophyceae) in the north Atlantic Ocean, it appeared possible to distinguish 10 phytogeographic distribution groups of wide applicability. Experimentally determined critical temperatures limiting essential events in the life histories of 17 benthic algal species were used to infer possible phytogeographic boundaries; these appeared to fit closely the phytogeographic boundaries derived from field-distribution data. For a temperate species, at least six different boundaries can be postulated and should be checked in the northern hemisphere: (1) the ‘northern lethal boundary’ (corresponding to the lowest winter temperature which a species can survive); (2) the ‘northern growth boundary’ (corresponding to the lowest summer temperature which, over a period of several months, permits sufficient growth); (3) the ‘northern reproductive boundary’ (corresponding to the lowest summer temperature permitting reproduction over a period of several months); (4–6) the corresponding southern boundaries. Photoperiodic responses may influence the temperature responses. Many phytogeographic boundaries appear to be of a composite nature. For instance, the southern boundary of Laminaria digitata follows the European 10°C February isotherm (which corresponds to the highest winter temperature permitting fertility in the female gametophyte, i.e. to the ‘southern reproductive boundary’), and the American 19°C summer isotherm (corresponding to the ‘southern lethal boundary’). Thus, experimental evidence supports the validity of eight of the following 10 distribution groups (for distribution groups 2 and 6, such evidence could not be found): (1) the amphiatlantic tropical-to-warm temperate group, with a north-eastern extension (examples: Gracilaria foliifera and Centroceras clavulalum); (2) the amphiatlantic tropical-to-warm temperate group, with a north-western extension (example: Hypnea musciformis); (3) the amphiatlantic tropical-to-temperate group (example: Sphacelaria rigidula =furcigera); (4) the amphiatlantic temperate group: the Cladophora rupestris type (examples: Callithamnion hookeri, Dumontia contorta; Laminaria saccharina is transitional to type 10, I., digitata to types 5 and 10); (5) the amphiatlantic temperate group: the Cl. albida type (examples: Scytosiphon lomentaria, Petalonia fascia); (6) the tropical western Atlantic group; (7) the north-east American tropical-to-temperate group (example: Gracilaria tikvahiae); (8) the north-east American temperate group and the corresponding Japanese temperate group (examples: Campylaephora hypneoides and Sargassum muticum); (9) the warm-temperate Mediterranean-Atlantic group, and the corresponding warm-temperate Californian group (examples: Saccorhiza polyschides, Laminaria hyperborea, I., ockroleuca, Macrocystis pyrifera, Hedophyllum sessile); (10) the Arctic group (examples: Saccorhiza dermatodea and Sphacelaria arctica). Distribution groups 6, 9 and 10 have comparatively narrow temperature ranges with a span of 18 22°C between their lethal boundaries and of 5 12°C between their reproductive or growth boundaries. These narrow temperature ranges limit the species in these groups to the tropics; the temperate coasts on the eastern sides of the north Pacific and north Atlantic Oceans and in the southern hemisphere; and to the Arctic, respectively. The narrow temperature ranges of group 9 make the species in this group unfit for life on the western temperate coasts of the north Pacific and north Atlantic Oceans, where algae must cope with annual temperature fluctuations of more than 20°C. Conversely, algae in group 8 (containing the numerous Japanese endemic species) are characterized by wide temperature spans (e.g. 29°C between ‘lethal boundaries’, 12–19°C between ‘growth and/or reproductive boundaries’) and must be potentially capable of occupying wide latitudinal belts on temperate coasts along the east sides of the north Pacific and north Atlantic Oceans. Algae ‘escaped’ from Japan, such as Sargassum muticum, conform to this picture. Apparently Japanese algae do not have the capacity for long distance dispersal. The corresponding east American coasts (30–45 N) harbour very few endemic species, probably as a result of the adverse nature of these sediment coasts for benthic macroalgae and their functioning as a barrier to latitudinal displacements of the flora during glaciations. The remaining distribution groups (1,2,3,4,5,7) are characterized by wide temperature spans and wide distributions, often in both the Atlantic and Pacific Oceans and in both hemispheres. Six temperate species (in distribution groups 4, 5 and 9) with an amphiaequatorial distribution have similar winter-temperature maxima permitting reproduction and corresponding with winter isotherms of 15–17°C; their upper lethal temperatures are more dissimilar and correspond with summer isotherms of 20–30°C. Their amphiaequatorial distribution can be explained by assuming glacial temperature drops along east Pacific and east Atlantic equatorial coasts in narrow belts of intensified upwelling during the presumably intensified glacial circulation of the ocean gyres.     

Population structure of the dusky pipefish (Syngnathus floridae) from the Atlantic and Gulf of Mexico,as revealed by mitochondrial DNA and microsatellite analyses

Aim To elucidate the historical phylogeography of the dusky pipefish (Syngnathus floridae) in the North American Atlantic and Gulf of Mexico ocean basins. Location Southern Atlantic Ocean and northern Gulf of Mexico within the continental United States. Methods A 394‐bp fragment of the mitochondrial cytochrome b gene and a 235‐bp fragment of the mitochondrial control region were analysed from individuals from 10 locations. Phylogenetic reconstruction, haplotype network, mismatch distributions and analysis of molecular variance were used to infer population structure between ocean basins and time from population expansion within ocean basins. Six microsatellite loci were also analysed to estimate population structure and gene flow among five populations using genetic distance methods (F_ST, Nei’s genetic distance), isolation by distance (Mantel’s test), coalescent‐based estimates of genetic diversity and migration patterns, Bayesian cluster analysis and bottleneck simulations. Results Mitochondrial analyses revealed significant structuring between ocean basins in both cytochrome b (Φ_ST = 0.361, P < 0.0001; Φ_CT = 0.312, P < 0.02) and control region (Φ_ST = 0.166, P < 0.0001; Φ_CT = 0.128, P < 0.03) sequences. However, phylogenetic reconstructions failed to show reciprocal monophyly in populations between ocean basins. Microsatellite analyses revealed significant population substructuring between all locations sampled except for the two locations that were in closest proximity to each other (global F_ST value = 0.026). Bayesian analysis of microsatellite data also revealed significant population structuring between ocean basins. Coalescent‐based analyses of microsatellite data revealed low migration rates among all sites. Mismatch distribution analysis of mitochondrial loci supports a sudden population expansion in both ocean basins in the late Pleistocene, with the expansion of Atlantic populations occurring more recently. Main conclusions Present‐day populations of S. floridae do not bear the mitochondrial DNA signature of the strong phylogenetic discontinuity between the Atlantic and Gulf coasts of North America commonly observed in other species. Rather, our results suggest that Atlantic and Gulf of Mexico populations of S. floridae are closely related but nevertheless exhibit local and regional population structure. We conclude that the present‐day phylogeographic pattern is the result of a recent population expansion into the Atlantic in the late Pleistocene, and that life‐history traits and ecology may play a pivotal role in shaping the realized geographical distribution pattern of this species.     

Embryonic development of the false limpet Siphonaria lateralis from Atlantic Patagonia

Siphonariids are pulmonate gastropods inhabiting rocky intertidal habitats, and many studies have focused on these false limpets around the world. In the southern South Atlantic, studies on reproduction and development in species of Siphonaria are scarce. We studied the embryonic development and egg masses of Siphonaria lateralis at its northernmost distribution in Atlantic Patagonia. In S. lateralis, as in most species of Siphonaria, individuals spawn benthic egg masses that strongly attach to intertidal rocky substrata. A single spherical egg that measures ~120 µm develops inside the egg capsule of S. lateralis. Considering the relatively small egg size, and reports from previous studies, the developmental modality of S. lateralis might be expected to include a planktotrophic larval phase. However, we found that hatchlings emerged as 1‐mm crawling juveniles, probably owing to the presence of intracapsular fluid, which may provide the energetic requirements for direct development. The embryonic size changed little from the egg to veliger stages, and then increased rapidly until the hatchling stage. We compared development in S. lateralis with development in the sympatric Siphonaria lessonii, in which egg size was reported to be ~80 µm and hatching occurs as planktotrophic veliger larvae. In these two species, spawn and early intracapsular developmental modes are remarkably different; these differences represent contrasting ways to survive in the harsh and physically stressful intertidal Patagonian coasts.     

Craniometric variation of some Mediterranean and Atlantic populations of Stenella coeruleoalba (Mammalia,Delphinidae): A three‐dimensional geometric morphometric analysis

The variability of cranial features of Atlantic and Mediterranean samples of Stenella coeruleoalba was examined using a three‐dimensional geometric morphometric approach. Data were collected on 79 skulls from the upper and middle Mediterranean Sea, the Atlantic French coasts, and Scotland. Three‐dimensional x, y, and z coordinates of 27 landmarks were recorded on each left half skull using a Microscribe 3‐D digitizer. All configurations were rotated, centered, and scaled, and residuals from the mean configuration were analyzed through multivariate analyses of variance. Mahalanobis distances among populations were used to evaluate phenetic relationships. Consensus configurations were compared to visualize shape differences among samples. Analyses revealed significant differences among populations, a clear distinction of the Scottish coasts dolphins from the other samples, and a closer relationship of the dolphins from the French coasts to the Mediterranean populations than to the Scottish one. Shape differences are mainly concentrated in the rostral and in the occipital regions of the skull. Phylogenetic and adaptive factors were invoked as possible causes of the variation patterns.     

Issue Information

Aeolidia papillosa (Linnaeus, 1761 ) is a well‐known aeolidiid species that has been reported to have a worldwide distribution in cold–temperate waters, mainly from the northern hemisphere. Molecular tools have recently shown that most cosmopolitan species usually belong to a taxonomic species complex. Here we used integrative taxonomy to test the range of distribution of A. papillosa, and to assess the existence of a putative species complex that has been traditionally included as a single species under the name A. papillosa. Maximum‐likelihood and Bayesian analyses of partial DNA sequences of the mitochondrial cytochrome c oxidase subunit I and 16S rRNA genes, and the nuclear gene histone 3, were used to infer phylogenetic trees. Automatic Barcode Gap Discovery (ABGD) species delimitation analyses and morphological study complemented the phylogenetic approach. Our results show that A. papillosa is a cosmopolitan and an amphi‐Atlantic species, being distributed in the eastern and western Atlantic as well as in the eastern Pacific; however, some specimens from the UK and the Netherlands, together with specimens from Portugal, Galicia, and France, as well as the Californian and Oregon populations, emerge as two pseudocryptic species described herein: Aeolidia filomenae  sp. nov. and Aeolidia loui  sp. nov. , respectively. Finally, the specimens from Chilean coasts, previously attributed to A. papillosa, belong to a different species, Aeolidia campbellii (Cunningham, 1871 ), that is a senior synonym of Aeolidia serotina Bergh, 1873 .     

Oceanic dispersal barriers in a holoplanktonic gastropod

Pteropods, a group of holoplanktonic gastropods, are regarded as bioindicators of the effects of ocean acidification on open ocean ecosystems, because their thin aragonitic shells are susceptible to dissolution. While there have been recent efforts to address their capacity for physiological acclimation, it is also important to gain predictive understanding of their ability to adapt to future ocean conditions. However, little is known about the levels of genetic variation and large‐scale population structuring of pteropods, key characteristics enabling local adaptation. We examined the spatial distribution of genetic diversity in the mitochondrial cytochrome c oxidase I (COI) and nuclear 28S gene fragments, as well as shell shape variation, across a latitudinal transect in the Atlantic Ocean (35°N–36°S) for the pteropod Limacina bulimoides. We observed high levels of genetic variability (COI π = 0.034, 28S π = 0.0021) and strong spatial structuring (COI Φ_ST = 0.230, 28S Φ_ST = 0.255) across this transect. Based on the congruence of mitochondrial and nuclear differentiation, as well as differences in shell shape, we identified a primary dispersal barrier in the southern Atlantic subtropical gyre (15–18°S). This barrier is maintained despite the presence of expatriates, a gyral current system, and in the absence of any distinct oceanographic gradients in this region, suggesting that reproductive isolation between these populations must be strong. A secondary dispersal barrier supported only by 28S pairwise Φ_ST comparisons was identified in the equatorial upwelling region (between 15°N and 4°S), which is concordant with barriers observed in other zooplankton species. Both oceanic dispersal barriers were congruent with regions of low abundance reported for a similar basin‐scale transect that was sampled 2 years later. Our finding supports the hypothesis that low abundance indicates areas of suboptimal habitat that result in barriers to gene flow in widely distributed zooplankton species. Such species may in fact consist of several populations or (sub)species that are adapted to local environmental conditions, limiting their potential for adaptive responses to ocean changes. Future analyses of genome‐wide diversity in pteropods could provide further insight into the strength, formation and maintenance of oceanic dispersal barriers.     

Distribution of saltmarsh plant communities associated with environmental factors along a latitudinal gradient on the south‐west Atlantic coast

Aim To produce an inventory of south‐west Atlantic saltmarshes (from latitude 31°48′ S to 43°20′ S) using remotely sensed images and field sampling; to quantify their total area; to describe the biogeographical variation of the main habitats characterized by dominant vascular plants, in relation to major environmental factors; to test the hypothesis of predominance of the reversal pattern in plant distribution (sedges and grasses dominate the lower, regularly inundated zones, while the upper zones are occupied by more halophytic species) previously described; and to compare these south‐west Atlantic saltmarshes with others world‐wide. Location South‐western Atlantic saltmarshes Methods Field samples of dominant emergent plant species positioned by the global positioning system (GPS) were obtained from most coastal saltmarshes (14) between southern Brazil and northern Patagonia, Argentina. Landsat satellite images were obtained and coastal saltmarsh habitats were quantified by supervised classification, utilizing points gathered in the field. Results Three main plant species dominated the low and middle intertidal saltmarsh, Spartina alterniflora Loesel., Spartina densiflora Brong. and Sarcocornia perennis (P. Mill.) A.J. Scott. The total area of the studied coastal saltmarshes was 2133 km², comprising 380 km² of Sp. alterniflora marsh, 366 km² of Sp. densiflora marsh, 746 km² of Sar. perennis marsh and 641 km² of brackish marsh (dominated by Juncus acutus L., Juncus kraussii Hochst., Scirpus maritimus L., Scirpus americanus Pers. and Phragmites australis (Cav.) Trin.). Cluster analysis showed three habitat types: saltmarshes dominated by (1) Sp. densiflora and brackish species,(2) Sp. alterniflora and Sar. perennis and (3) Sp.densiflora only. The analysis of abiotic variables showed significant differences between groups of habitats and coordinated gradients of the abiotic variables. The south‐west Atlantic coast showed decreasing mean annual rainfall (1200 to 196 mm) and increasing mean tidal amplitude (< 0.5 to > 2.5 m) from latitude 31° to 43°. Main conclusions South‐west Atlantic saltmarshes are globally important by virtue of their total extent. Remote sensing showed that the reversal pattern in plant distribution is not widespread. Indeed, south‐west Atlantic saltmarshes are better characterized by the presence of the halophytic genera Spartina and Sarcocornia. Our results support the interpretation that south‐west Atlantic saltmarshes constitute a class of temperate type (sensu Adam, 1990 ) with transitional characteristics between Australasian–South African saltmarshes and west Atlantic saltmarshes.     

Molecular phylogeny and biogeographic history of the European Maja spider crabs (Decapoda, Majidae)

We have assessed for the first time the phylogenetic relationships and biogeographic history of the crabs of the genus Maja that inhabit European coasts: M. brachydactyla, M. crispata, M. goltziana and M. squinado. Using mitochondrial markers, we have recovered a well-resolved phylogenetic tree that supports a single origin for the European species, most likely from an Indo-West Pacific ancestor during the Early Miocene. In this phylogeny, M. goltziana appears as the basal European species, with a sister lineage bifurcating into an Eastern Atlantic (M. brachydactyla) and a Mediterranean (M. crispata and M. squinado) clade. We propose the Tethyan Seaway as the initial colonization route, although an entrance through South Africa cannot be discounted. The Eastern Atlantic/Mediterranean split seems to predate the Messinian salinity crisis, which, in turn, could have promoted the recent divergence within the Mediterranean. In addition, Pleistocene glaciations could explain the current diversity in the Eastern Atlantic Ocean, where a unique mitochondrial lineage is found. According to this, the genetic profile of South African crabs appears to belong to M. brachydactyla, questioning the validity of the putative species M. capensis.     

Physicochemical environments and tolerances of cyprinodontoid fishes found in estuaries and salt marshes of eastern North America

Individuals of 28 species of cyprinodontoid fishes have been reported from estuaries/salt marshes of the Atlantic and Gulf coasts of North America. Some species show limited latitudinal distributions and/or occupy a limited range of habitats; others are widely distributed and/or occupy a wide range of habitats.A literature survey was made of conditions of water temperature, dissolved-oxygen (DO) concentrations, and salinities at sites where individuals of each species had been collected, and of laboratory-determined tolerances or lethal limits and other responses to those abiotic conditions. Individuals of Cyprinodon variegatus showed the widest overall range of tolerance of environmental temperatures, −1.9–45.4°C, with Gambusia rhizophorae showing the highest lower temperature-tolerance limit, 17°C. The only species highly sensitive to hypoxia was Floridichthys carpio, which showed “stress” at DO levels of 6–8 mg kg⁻¹. All showed use of aquatic surface respiration, except for Kryptolebias marmoratus, which uses aerial respiration in the presence of H₂S, and/or under hypoxic conditions. Individuals of C. variegatus were found to tolerate ambient salinities ranging from < 0.5 to 125.2, or higher, and several species of the genus Fundulus were found to tolerate concentrations ranging from <0.5 to ≥100. However, some of the species discussed cannot tolerate salinities beyond those of dilute brackish waters. In most instances, laboratory-determined tolerance limits of temperature and salinity were wider than conditions under which individuals of these species had been found in nature. The majority of available information related to adult individuals, with few studies focused on immature stages; however, existing information permitted a brief review of spawning, incubation, and early development features in Fundulus heteroclitus.Suggestions were made, based on existing information, as to species that would be most likely to show altered population distributions resulting from continued global warming. These included five species that have tropical/subtropical, or subtropical/temperate distributions. Also, a few others were included that show extensive latitudinal distributions, most extending northward into cooler temperate regions of the Atlantic coast. At present, none of these species has shown a range alteration that can be attributed to global warming.