The endosymbiont community as taxonomic character: a novel approach to resolving the Bemisia tabaci complex

In this issue of Molecular Ecology, Gueguen et al. (2010) describe their novel approach to resolving cryptic genetic diversity in the Bemisia tabaci complex (Hemiptera: Aleyrodidae.) Complexes of cryptic species present a challenge to both morphological and molecular taxonomy – the former presumed, as shared morphology normally defines species as cryptic, but the latter also problematic when host DNA sequence data is either inconclusive or unaccompanied by independent evidence. Endosymbiont associations with insect hosts have, historically, complicated efforts to develop a robust molecular taxonomy, but the approach of Gueguen et al. takes advantage of endosymbiont community composition to help rather than hinder the task of resolving taxonomic distinctions within the B. tabaci complex.     

Cryptic diversity and patterns of host specificity in trematode flatworms

The widespread utilization of molecular markers has revealed that a broad spectrum of taxa contain sets of morphologically cryptic, but genetically distinct lineages ( Bickford et al. 2007 ). The identification of cryptic taxa is important as an accurate appreciation of diversity is crucial for a proper understanding of evolutionary and ecological processes. An example is the study of host specificity in parasitic taxa, where an apparent generalist may be found to contain a complex of several more specific species ( Smith et al. 2006 ). Host specificity is a key life history trait that varies greatly among parasites ( Poulin & Keeney 2007 ). While some can exploit a wide range of hosts, others are confined to just a single species. Access to additional hosts increases the resources available to a parasite. However, physiological or ecological constraints can restrict the extension of host range. Furthermore, there may be a trade‐off between relaxed specificity and performance: generalism can decrease a parasites ability to adapt to each individual host species, and increase exposure to competition from other parasites ( Poulin 1998 ). Despite the central role that host specificity plays in parasite life history, relatively little is known about how host range is determined in natural systems, and data from field studies are required to evaluate among competing ideas. In this issue, an exciting paper by Locke et al. (2010) makes a valuable contribution toward the understanding of host specificity in an important group of trematode flatworms. Using molecular methods, Locke et al. reveal an almost four‐fold increase in the appreciated diversity of their focal group. In combination with a large and elegant sampling design this allows them to accurately assess host specificity for each taxon, and thus draw key insights into the factors that control host range in a dominant parasite group.     

High‐throughput SNPs for all: genotyping‐in‐thousands

Understanding the genetic structure of species is essential for conservation. It is only with this information that managers, academics, user groups and land‐use planners can understand the spatial scale of migration and local adaptation, source‐sink dynamics and effective population size. Such information is essential for a multitude of applications including delineating management units, balancing management priorities, discovering cryptic species and implementing captive breeding programmes. Species can range from locally adapted by hundreds of metres (Pavey et al. 2010 ) to complete species panmixia (Côté et al. 2013 ). Even more remarkable is that this essential information can be obtained without fully sequenced or annotated genomes, but from mere (putatively) nonfunctional variants. First with allozymes, then microsatellites and now SNPs, this neutral genetic variation carries a wealth of information about migration and drift. For many of us, it may be somewhat difficult to remember our understanding of species conservation before the widespread usage of these useful tools. However most species on earth have yet to give us that ‘peek under the curtain’. With the current diversity on earth estimated to be nearly 9 million species (Mora et al. 2011 ), we have a long way to go for a comprehensive meta‐phylogeographic understanding. A method presented in this issue by Campbell and colleagues (Campbell et al. 2015 ) is a tool that will accelerate the pace in this area. Genotyping‐in‐thousands (GT‐seq) leverages recent advancements in sequencing technology to save many hours and dollars over previous methods to generate this important neutral genetic information.     

Morphological Characterizations of Four Species of Parallelostrombidium (Ciliophora,Oligotrichia), with a Note on the Phylogeny of the Genus

The morphology and phylogeny of four oligotrichid ciliates, Parallelostrombidium paraellipticum sp. n., P. dragescoi sp. n., P. jankowskii (Xu et al. 2009) comb. n., and P. kahli (Xu et al. 2009) comb. n., are described or redescribed based on live observation, protargol stained material, and SSU rRNA gene sequences. The new species P. paraellipticum sp. n. is characterized by its obovoidal cell shape, adoral zone composed of 17–21 collar, 9–11 buccal, and two thigmotactic membranelles, and extrusomes attached in one row along the girdle kinety. The new species P. dragescoi sp. n. is distinguished from its congeners by its obovoidal cell shape and a lack of thigmotactic membranelles. Based on ciliary patterns recognizable in the original slides, Omegastrombidium jankowskii Xu et al. 2009 and O. kahli Xu et al. 2009 should be transferred to the genus Parallelostrombidium Agatha 2004. Phylogenetic analyses based on SSU rRNA gene sequence data demonstrate that all four new sequences cluster with previously described congeners. The genus Parallelostrombidium is separated into two clusters, suggesting its non‐monophyly and probably corresponding to the two subgenera proposed by Agatha and Strüder‐Kypke (2014), as well as their morphological difference (cell dorsoventrally flattened vs. unflattened).     

Phylogenomics and multigene phylogenies decipher two new cryptic marine algae from California,Gelidium gabrielsonii and G. kathyanniae (Gelidiales,Rhodophyta)

Molecular surveys are leading to the discovery of many new cryptic species of marine algae. This is particularly true for red algal intertidal species, which exhibit a high degree of morphological convergence. DNA sequencing of recent collections of Gelidium along the coast of California, USA, identified two morphologically similar entities that differed in DNA sequence from existing species. To characterize the two new species of Gelidium and to determine their evolutionary relationships to other known taxa, phylogenomic, multigene analyses, and morphological observations were performed. Three complete mitogenomes and five plastid genomes were deciphered, including those from the new species candidates and the type materials of two closely related congeners. The mitogenomes contained 45 genes and had similar lengths (24,963–24,964 bp). The plastid genomes contained 232 genes and were roughly similar in size (175,499–177,099 bp). The organellar genomes showed a high level of gene synteny. The two Gelidium species are diminutive, turf‐forming, and superficially resemble several long established species from the Pacific Ocean. The phylogenomic analysis, multigene phylogeny, and morphological evidence confirms the recognition and naming of two new species, describe herein as G. gabrielsonii and G. kathyanniae. On the basis of the monophyly of G. coulteri, G. gabrielsonii, G. galapagense, and G. kathyanniae, we suggest that this lineage likely evolved in California. Organellar genomes provide a powerful tool for discovering cryptic intertidal species and they continue to improve our understanding of the evolutionary biology of red algae and the systematics of the Gelidiales.     

A clarification of Pouydebat et al., 2008, evolution of grasping among anthropoids

Several statements by Pouydebat et al. (2008) do not adequately represent views of authors cited, in part because they reflect confusion in the literature about terminology regarding precision gripping. We address these problems, by tracing definitions of precision grips through the literature on manipulative behaviour and identifying the grip that is central to the Pouydebat et al. (2008) study. This allows us to offer a clarification of the statements by Pouydebat et al. (2008) regarding the sequence of appearance of human grip capabilities and possible morphological correlates to these capabilities in extant species.     

Cryptic speciation in the field vole: a multilocus approach confirms three highly divergent lineages in Eurasia

Species are generally described from morphological features, but there is growing recognition of sister forms that show substantial genetic differentiation without obvious morphological variation and may therefore be considered ‘cryptic species’. Here, we investigate the field vole (Microtus agrestis), a Eurasian mammal with little apparent morphological differentiation but which, on the basis of previous sex‐linked nuclear and mitochondrial DNA (mtDNA) analyses, is subdivided into a Northern and a Southern lineage, sufficiently divergent that they may represent two cryptic species. These earlier studies also provided limited evidence for two major mtDNA lineages within Iberia. In our present study, we extend these findings through a multilocus approach. We sampled 163 individuals from 46 localities, mainly in Iberia, and sequenced seven loci, maternally, paternally and biparentally inherited. Our results show that the mtDNA lineage identified in Portugal is indeed a distinct third lineage on the basis of other markers as well. In fact, multilocus coalescent‐based methods clearly support three separate evolutionary units that may represent cryptic species: Northern, Southern and Portuguese. Divergence among these units was inferred to have occurred during the last glacial period; the Portuguese lineage split occurred first (estimated at c. 70 000 bp ), and the Northern and Southern lineages separated at around the last glacial maximum (estimated at c. 18 500 bp ). Such recent formation of evolutionary units that might be considered species has repercussions in terms of understanding evolutionary processes and the diversity of small mammals in a European context.     

Sperm dispersal distances estimated by parentage analysis in a brooding scleractinian coral

Within populations of brooding sessile corals, sperm dispersal constitutes the mechanism by which gametes interact and mating occurs, and forms the first link in the network of processes that determine specieswide connectivity patterns. However, almost nothing is known about sperm dispersal for any internally fertilizing coral. In this study, we conducted a parentage analysis on coral larvae collected from an area of mapped colonies, to measure the distance sperm disperses for the first time in a reef‐building coral and estimated the mating system characteristics of a recently identified putative cryptic species within the Seriatopora hystrix complex (ShA; Warner et al. 2015). We defined consensus criteria among several replicated methods (colony 2.0, cervus 3.0, mltr v3.2) to maximize accuracy in paternity assignments. Thirteen progeny arrays indicated that this putative species produces exclusively sexually derived, primarily outcrossed larvae (mean t_m = 0.999) in multiple paternity broods (mean r_p = 0.119). Self‐fertilization was directly detected at low frequency for all broods combined (2.8%), but comprised 23% of matings in one brood. Although over 82% of mating occurred between colonies within 10 m of each other (mean sperm dispersal = 5.5 m ± 4.37 SD), we found no evidence of inbreeding in the established population. Restricted dispersal of sperm compared to slightly greater larval dispersal appears to limit inbreeding among close relatives in this cryptic species. Our findings establish a good basis for further work on sperm dispersal in brooding corals and provide the first information about the mating system of a newly identified and abundant cryptic species.     

Polymorphism in a common Atlantic reef coral (Montastraea cavernosa) and its long-term evolutionary implications

Recent advances in morphometrics and genetics have led to the discovery of numerous cryptic species in coral reef ecosystems. A prime example is the Montastraea annularis scleractinian coral species complex, in which morphological, genetic, and reproductive data concur on species boundaries, allowing evaluation of long-term patterns of speciation and evolutionary innovation. Here we test for cryptic species in the Atlantic species, Montastraea cavernosa, long recognized as polymorphic. Our modern samples consist of 94 colonies collected at four locations (Belize, Panamá, Puerto Rico in the Caribbean; S?o Tomé in the Eastern Atlantic). Our fossil samples consist of 78 colonies from the Plio-Pleistocene of Costa Rica and Panamá. Landmark morphometric data were collected on thin sections of 46 modern and 78 fossil colonies. Mahalanobis distances between colonies were calculated using Bookstein coordinates, revealing two modern and four fossil morphotypes. The remaining 48 of the 94 modern colonies were assigned to morphotype using discriminant analysis of calical measurements. Cross-tabulation and multiple comparisons tests show no significant morphological differences among geographic locations or water depths. Patterns of variation within and among fossil morphotypes are similar to modern morphotypes. DNA sequence data were collected for two polymorphic nuclear loci (β-tub1 and β-tub2) on all 94 modern colonies. Haplotype networks show that both genes consist of two clades, but morphotypes are not associated with genetic clades. Genotype frequencies and two-locus genotype assignments indicate genetic exchange across clades, and ϕst values show no genetic differentiation between morphotypes at different locations. Taken together, our morphological and genetic results do not provide evidence for cryptic species in M. cavernosa, but indicate instead that this species has an unusually high degree of polymorphism over a wide geographic area and persisting for >25 million years (myr).     

Distance from forest edge affects bee pollinators in oilseed rape fields

Wild pollinators have been shown to enhance the pollination of Brassica napus (oilseed rape) and thus increase its market value. Several studies have previously shown that pollination services are greater in crops adjoining forest patches or other seminatural habitats than in crops completely surrounded by other crops. In this study, we investigated the specific importance of forest edges in providing potential pollinators in B. napus fields in two areas in France. Bees were caught with yellow pan traps at increasing distances from both warm and cold forest edges into B. napus fields during the blooming period. A total of 4594 individual bees, representing six families and 83 taxa, were collected. We found that both bee abundance and taxa richness were negatively affected by the distance from forest edge. However, responses varied between bee groups and edge orientations. The ITD (Inter‐Tegular distance) of the species, a good proxy for bee foraging range, seems to limit how far the bees can travel from the forest edge. We found a greater abundance of cuckoo bees (Nomada spp.) of Andrena spp. and Andrena spp. males at forest edges, which we assume indicate suitable nesting sites, or at least mating sites, for some abundant Andrena species and their parasites (Fig.  1 ). Synthesis and Applications. This study provides one of the first examples in temperate ecosystems of how forest edges may actually act as a reservoir of potential pollinators and directly benefit agricultural crops by providing nesting or mating sites for important early spring pollinators. Policy‐makers and land managers should take forest edges into account and encourage their protection in the agricultural matrix to promote wild bees and their pollination services.

Figure 1 Open in figure viewer PowerPoint Left, a Nomada sp male; right, an Andrena sp male. Caption Left, a Nomada sp male; right, an Andrena sp male.

Introduction

Pollinators play an important functional role in most terrestrial ecosystems and provide a key ecosystem service (Ashman et al. 2004 ). Insects, particularly bees, are the primary pollinators for the majority of the world's angiosperms (Ollerton et al. 2012 ). Without this service, many interconnected species and processes functioning within both wild and agricultural ecosystems could collapse (Kearns et al. 1998 ). Brassica napus (oilseed rape, OSR) represents the most widespread entomophilous crop in France with almost 1.5 Mha in 2010 (FAOSTAT August 10th, 2012). Results differ between varieties, but even though it seems that OSR produces 70% of its fruits through self‐pollination (Downey et al. 1970 in Mesquida and Renard 1981 ), native bees are also known to contribute to its pollination (Morandin and Winston 2005 ; Jauker et al. 2012 ). Bee pollination leads to improved yields (Steffan‐Dewenter 2003b ; Sabbahi et al. 2005 ) and to a shorter blooming period (Sabbahi et al. 2006 ), thus increasing the crop's market value (Bommarco et al. 2012 ). The most widely used species in crop pollination is the honeybee (Apis mellifera L) which is sometimes assumed to be sufficient for worldwide crop pollination (Aebi and Neumann 2011 ). However, this assertion has been questioned by different authors (Ollerton et al. 2012 ), and several studies show that many wild bees are also efficient pollinators of crops (Klein et al. 2007 ; Winfree et al. 2008 ; Breeze et al. 2011 ). Recently, Garibaldi et al. ( 2013 ) found positive associations of fruit set with wild‐insect visits to flowers in 41 crop systems worldwide. They demonstrate that honeybees do not maximize pollination, nor can they fully replace the contributions of diverse, wild‐insect assemblages to fruit set for a broad range of crops and agricultural practices on all continents with farmland. Unfortunately, not only are honey bees declining due to a variety of different causes (vanEngelsdorp et al. 2009 ), wild bee populations are also dwindling (Potts et al. 2010 ). Their decline has been documented in two Western European countries (Britain and the Netherlands) by comparing data obtained before and after 1980 (Biesmeijer et al. 2006 ). These losses have mostly been attributed to the use of agrochemicals, the increase in monocultures, the loss of seminatural habitat and deforestation (Steffan‐Dewenter et al. 2002 ; Steffan‐Dewenter and Westphal 2008 ; Brittain and Potts 2011 ). Several studies have shown the importance of natural or seminatural habitats in sustaining pollinator populations or pollination services close to fruit crops (Steffan‐Dewenter 2003a ; Kremen et al. 2004 ; Greenleaf and Kremen 2006a ; Carvalheiro et al. 2010 ). Morandin and Winston ( 2006 ) presented a cost–benefit model that estimates profit in OSR agroecosystems with different proportions of uncultivated land. They calculated that yield and profit could be maximized with 30% of the land left uncultivated within 750 m of field edges. Other studies have demonstrated a negative impact of the distance from forests on pollination services or bee abundance and richness both in tropical ecosystems (De Marco and Coelho 2004 ; Blanche et al. 2006 ; Chacoff and Aizen 2006 ) and in temperate ecosystems (Hawkins 1965 ; Taki et al. 2007 ; Arthur et al. 2010 ; Watson et al. 2011 ). These studies all suggest that natural or seminatural habitats are important sources of pollinators, probably because they provide “partial habitats” (Westrich 1996 ) such as complementary mating, foraging, nesting, and nesting materials sites that bees need to complete their life cycle. In this study, we focused on the effect of distance to forest edge on bee assemblages in OSR ecosystems. Forest edges could provide one or more important partial habitats for different bee species in agricultural landscapes, in particular when associated with a mass‐flowering crop such as OSR (Le Feon et al. 2011 ). For example, the availability of untilled soil and dead branches might provide ground‐nesting and cavity‐nesting bee species with numerous nesting sites. Moreover, during spring at least, the understory and the forest edge can provide cover containing flowering plants and wild trees such as Prunus spp, Castanea sativa, or Salix spp and thereby allow bees to find alternative floral resources. During spring 2010 and 2011, in two areas in France, we examined wild bee abundance and taxa richness both along forest edges and inside OSR fields at different distances from the forest. Like other taxa, bees respond to environmental variables according to their biologic traits that determine access and requirements for nesting, mating, and forage resources, species mobility or physiological tolerance. Specifically, we hypothesized that (1) bee abundance, species richness, and composition of bee communities within the crop field are dependent on the distance from the forest edge (where complementary floral resources, nesting sites, shelters, etc. can be found) and on the orientation of the forest edge; (2) the identity of bees in the crop is related to their foraging range which we measured with the ITD (Inter‐Tegular distance); (3) the forest edge may be the nesting or mating sites for cavity‐nesting or ground‐nesting bees such as Osmia spp or Andrena spp which are important groups of potential early spring pollinators for OSR.     

Cryptic diversity in disjunct populations of Middle American Montane Pitvipers: a systematic reassessment of Cerrophidion godmani

Jadin, R.C., Townsend, J.H., Castoe, T.A. & Campbell, J.A. (2012). Cryptic diversity in disjunct populations of Middle American Montane Pitvipers: a systematic reassessment of Cerrophidion godmani. —Zoologica Scripta, 41, 455–470. The discovery and taxonomic recognition of cryptic species has become increasingly frequent with the application of molecular phylogenetic analyses, particularly for species with broad geographic distributions. In this study we focus on the venomous pitviper species Cerrophidion godmani that is widely distributed throughout the highlands of Central America. We provide evidence based on both molecular phylogenetic analyses and morphological data that C. godmani represents three deeply divergent lineages and is possibly non‐monophyletic. These three lineages are relatively conserved in their morphology and tend to be highly variable among individuals, but we do find sufficient morphological characters to diagnose them as evolutionarily distinct. We apply these data, together with known geographic distributions of populations, to infer boundaries of these three divergent evolutionary lineages. Based on the body of evidence, we formally name and describe two new species of Cerrophidion and redescribe C. godmani sensu stricto.     

Orobothriurus (Scorpiones: Bothriuridae) phylogeny,Andean biogeography,and the relative importance of genitalic and somatic characters

Mattoni, C.I., Ochoa, J.A., Ojanguren Affilastro, A.A. & Prendini, L. (2012) Orobothriurus (Scorpiones: Bothriuridae) phylogeny, Andean biogeography, and the relative importance of genitalic and somatic characters. —Zoologica Scripta, 41, 160–176. The genus Orobothriurus Maury, 1976 (Bothriuridae Simon, 1880) displays an Andean pattern of distribution, most of its species occurring at high altitudes (over 2000–2500 m to a maximum altitude record of 4910 m) from central Peru to Argentina. The recent discovery of several new species and the uncertain phylogenetic position of Orobothriurus lourencoi Ojanguren Affilastro, 2003, required a reanalysis of Orobothriurus phylogeny. Thirty bothriurid taxa, including all species of Orobothriurus and Pachakutej Ochoa, 2004, were scored for 65 morphological characters and analysed with parsimony under equal and implied weighting. The resulting topology justifies the establishment of a new genus, Rumikiru Ojanguren Affilastro et al., in press , for O. lourencoi and a closely related, new species, Rumikiru atacama Ojanguren Affilastro et al., in press . It also offers new insights about the phylogeny and biogeography of Orobothriurus and related genera. Characters from the male genitalia (i.e. hemispermatophore), comprising approximately 26% of the morphological matrix, were found to be less homoplastic than those from somatic morphology, contradicting suggestions that genitalia are uninformative or potentially misleading in phylogenetic studies.     

Identification and characterization of microsatellites loci in Brycon opalinus (Cuvier, 1819) (Characiforme,Characidae, Bryconiae)

Brycon species are present in various basins in Brazil and were or still are part of commercial fisheries and aquaculture activities ( Ferreira et al. 1996 , Mendonça 1994 ). Despite the importance of this group of fish, natural populations of some Brycon species are endangered ( Lins et al. 1997 ). Here, we describe the characterization of seven microsatellite loci that will be useful for the genetic studies in natural and captive populations for these and other species of Brycon.     

Molecular patterns of differentiation in canyon treefrogs (Hyla arenicolor): evidence for introgressive hybridization with the Arizona treefrog (H. wrightorum) and correlations with advertisement call differences

Detection of genetic and behavioural diversity within morphologically similar species has led to the discovery of cryptic species complexes. We tested the hypothesis that US populations of the canyon treefrog (Hyla arenicolor) may consist of cryptic species by examining mate‐attraction signals among three divergent clades defined by mtDNA. Using a multi‐locus approach, we re‐analysed phylogenetic relationships among the three clades and a closely related, but morphologically and behaviourally dissimilar species, the Arizona treefrog (H. wrightorum). We found evidence for introgression of H. wrightorum’s mitochondrial genome into H. arenicolor. Additionally, the two‐clade topology based on nuclear data is more congruent with patterns of call variation than the three‐clade topology from the mitochondrial dataset. The magnitude of the call divergence is probably insufficient to promote isolation of the nuclear DNA‐defined clades should they become sympatric, but further divergence in call properties significant in species identification could promote speciation in the future.     

Exploiting plants for glutathione (GSH) production: Uncoupling GSH synthesis from cellular controls results in unprecedented GSH accumulation

Glutathione (GSH) is a key factor for cellular redox homeostasis and tolerance against abiotic and biotic stress ( May et al., 1998 ; Noctor et al., 1998a ). Previous attempts to increase GSH content in plants have met with moderate success ( Rennenberg et al., 2007 ), largely because of tight and multilevel control of its biosynthesis ( Rausch et al., 2007 ). Here, we report the in planta expression of the bifunctional γ‐glutamylcysteine ligase—glutathione synthetase enzyme from Streptococcus thermophilus (StGCL‐GS), which is shown to be neither redox‐regulated nor sensitive to feedback inhibition by GSH. Transgenic tobacco plants expressing StGCL‐GS under control of a constitutive promoter reveal an extreme accumulation of GSH in their leaves (up to 12 μmol GSH/gFW, depending on the developmental stage), which is more than 20‐ to 30‐fold above the levels observed in wild‐type (wt) plants and which can be even further increased by additional sulphate fertilization. Surprisingly, this dramatically increased GSH production has no impact on plant growth while enhancing plant tolerance to abiotic stress. Furthermore, StGCL‐GS‐expressing plants are a novel, cost‐saving source for GSH production, being competitive with current yeast‐based systems ( Li et al., 2004 ).     

Using DNA taxonomy to investigate the ecological determinants of plankton diversity: explaining the occurrence of Synchaeta spp. (Rotifera,Monogononta) in mountain lakes

1. The occurrence of unresolved complexes of cryptic species may hinder the identification of the main ecological drivers of biodiversity when different cryptic taxa have different ecological requirements. 2. We assessed factors influencing the occurrence of Synchaeta species (monogonont rotifers) in 17 waterbodies of the Trentino‐South Tyrol region in the Eastern Alps. To do so, we compared the results of using unresolved complexes of cryptic species, as is common practice in limnological studies based on morphological taxonomy, and having resolved cryptic complexes, made possible by DNA taxonomy. 3. To identify cryptic species, we used the generalised mixed Yule coalescent (GMYC) model. We investigated the relationship between the environment and the occurrence of Synchaeta spp. by multivariate ordination using two definitions of the units of diversity, namely (i) unresolved species complexes (morphospecies) and (ii) putative cryptic species (GMYC entities). Our expectation was that resolving complexes of cryptic species could provide more information than using morphospecies. 4. As expected, DNA taxonomy provided greater taxonomic resolution than morphological taxonomy. Further, environmental‐based multivariate ordination on cryptic species explained a significantly higher proportion of variance than that based on morphospecies. Occurrence of GMYC entities was related to total phosphorus (TP), whereas no relationship could be found between morphospecies and the environment. Moreover, different cryptic species within the same morphospecies showed different, and even opposite, preferences for TP. In addition, the wide geographical distribution of haplotypes and cryptic species indicated the absence of barriers to dispersal in Synchaeta.     

Molecular evolution of Cinetochilum and Sathrophilus (Protozoa,Ciliophora, Oligohymenophorea), two genera of ciliates with morphological affinities to scuticociliates

Zhang, Q., Miao, M., Strüder‐Kypke, M. C., Al‐Rasheid, K. A. S., Al‐Farraj, S. A. & Song, W. (2011). Molecular evolution of Cinetochilum and Sathrophilus (Protozoa, Ciliophora, Oligohymenophorea), two genera of ciliates with morphological affinities to scuticociliates. —Zoologica Scripta, 40, 317–325. The ciliate order Loxocephalida sensu Li et al. (2006) has been considered to be systematically uncertain within the subclass Scuticociliatia. Loxocephalids display mixed morphological features and morphogenetic patterns that are found in two different oligohymenophorean subclasses: scuticociliates and hymenostomes. To reveal their phylogenetic positions, molecular information on this group is urgently needed but still inadequate. In the present study, we have sequenced the small subunit rRNA gene of two newly described loxocephalids, Cinetochilum ovale Gong & Song 2008; and Sathrophilus planus Fan et al. 2010; which have never been discussed based on molecular analysis. Results show: (i) all phylogenetic trees are nearly identical in placing Cinetochilum closest to the subclass Apostomatia and form a monophyletic group divergent from the typical scuticociliates, (ii) the genus Sathrophilus, together with Anoplophrya, a poorly known Astomatia, forms a peripheral branch separated from the scuticociliatian assemblage and (iii) the affiliation of the loxocephalid genera sensu Li et al. (2006) is not confirmed due to a dispersion in four deeply diverged clades. In addition, the polyphyly of the genus Cyclidium, shown in previous studies, is confirmed by our phylogenetic analyses and supported by the approximately unbiased test based on the new database in this work.     

Deceleration of morphological evolution in a cryptic species complex and its link to paleontological stasis

Morphological stasis or the absence of morphological change is a well-known phenomenon in the paleontological record, yet it is poorly integrated with neontological evidence. Recent evidence suggests that cryptic species complexes may remain morphologically identical due to morphological stasis. Here, we describe a case of long-term stasis in the Stygocapitella cryptic species complex (Parergodrilidae, Orbiniida, Annelida). Using phylogenetic methods and morphological data, we find that rates of morphological evolution in Stygocapitella are significantly slower than in closely related taxa (Nerillidae, Orbiniidae). Assessment of quantitative and qualitative morphology revealed the presence of four morphotypes with only subtle differences, whereas molecular data supports 10 reproductively isolated clades. Notably, estimates for the time of Stygocapitella species divergence range from ∼275 million years to ∼18 million years, including one case of two morphologically similar species that have diverged about 140 million years ago. These findings provide evidence for morphological deceleration and long-term morphological stasis in Stygocapitella, and that speciation is not necessarily accompanied by morphological changes. The deceleration of morphological divergence in Stygocapitella can be potentially linked to niche conservatism and tracking, coupled with the fluctuating dynamics of the interstitial environment, or genetic constraints due to progenetic evolution. Finally, we conclude that failing to integrate speciation without morphological evolution in paleontology may bias estimates of rates of speciation and morphological evolution.     

Taxonomic implications for diaptomid copepods based on contrasting patterns of mitochondrial DNA sequence divergences in four morphospecies

Morphological identification methods do not provide reliable and meaningful species identifications for taxa where morphological differences among distinct species are either absent or overlooked (i.e., cryptic species). For example, due to the minute nature of the morphological characters used to delineate diaptomid copepod species and the apparent potential for copepod speciation to occur with little or no morphological change (i.e., morphological stasis), morphological identifications of diaptomid species may not adequately capture their true species diversity. Here, we present results from a geographic survey of mtDNA sequences from populations across the geographic ranges of four North American diaptomid species—Leptodiaptomus minutus, Skistodiaptomus pallidus, Skistodiaptomus reighardi, and Onychodiaptomus sanguineus. Shallow mitochondrial DNA sequence divergences (maximum of 1.1%) among haplotypes of L. minutus from across its geographic range suggest that current morphological identification techniques reliably identify this species. In contrast, we found large mitochondrial DNA sequence divergences (14–22%) among populations within the currently recognized morphospecies of S. pallidus, S. reighardi, and O. sanguineus. However, pairwise sequence divergences within four distinct S. pallidus clades and within populations of S. reighardi and O. sanguineus were similarly low (maximum of 1.5%) as found within L. minutus as a whole. Thus, the S. pallidus, S. reighardi, and O. sanguineus morphospecies may be considered best as cryptic species complexes. Our study therefore indicates that morphological identifications, while sufficient for some species, likely underestimate the true species diversity of diaptomid copepods. As such, we stress the need for extensive taxonomic revision that integrates genetic, morphological, reproductive, and ecological analyses of this diverse and important group of freshwater zooplankton. Furthermore, we believe an extensive taxonomic revision will shed important insight into major questions regarding the roles of geography, phylogeny, and habitat on the frequency of cryptic species on earth. Handling editor: S. I. Dodson