Evolution of subterranean diving beetles (Coleoptera: Dytiscidae: Hydroporini, Bidessini) in the arid zone of Australia

Calcrete aquifers in arid inland Australia have recently been found to contain the world's most diverse assemblage of subterranean diving beetles (Coleoptera: Dytiscidae). In this study we test whether the adaptive shift hypothesis (ASH) or the climatic relict hypothesis (CRH) is the most likely mode of evolution for the Australian subterranean diving beetles by using a phylogeny based on two sequenced fragments of mitochondrial genes (CO1 and 16S-tRNA-ND1) and linearized using a relaxed molecular clock method. Most individual calcrete aquifers contain an assemblage of diving beetle species of distantly related lineages and/or a single pair of sister species that significantly differ in size and morphology. Evolutionary transitions from surface to subterranean life took place in a relatively small time frame between nine and four million years ago. Most of the variation in divergence times of the sympatric sister species is explained by the variation in latitude of the localities, which correlates with the onset of aridity from the north to the south and with an aridity maximum in the Early Pliocene (five mya). We conclude that individual calcrete aquifers were colonized by several distantly related diving beetle lineages. Several lines of evidence from molecular clock analyses support the CRH, indicating that all evolutionary transitions took place during the Late Miocene and Early Pliocene as a result of aridification.     

Speciation of Iberian diving beetles in Pleistocene refugia (Coleoptera, Dytiscidae)

The Mediterranean basin is an area of high diversity and endemicity, but the age and origin of its fauna are still largely unknown. Here we use species-level phylogenies based on approximately 1300 base pairs of the genes 16S rRNA and cytochrome oxidase I to establish the relationships of 27 of the 34 endemic Iberian species of diving beetles in the family Dytiscidae, and to investigate their level of divergence. Using a molecular clock approach, 18-19 of these species were estimated to be of Pleistocene origin, with four to six of them from the Late Pleistocene ( approximately 100 000 years). A second, lower speciation frequency peak was assigned to Late Miocene or Early Pliocene. Analysis of the distributional ranges showed that endemic species placed in the tip nodes of the trees are significantly more likely to be allopatric with their sisters than endemic species at lower node levels. Allopatric sister species are also significantly younger than sympatric clades, in agreement with an allopatric mode of speciation and limited subsequent range movement. These results strongly suggest that for some taxa Iberian populations were isolated during the Pleistocene long enough to speciate, and apparently did not expand their ranges to recolonize areas north of the Pyrenees. This is in contradiction to observations from fossil beetles in areas further north, which document large range movements associated with the Pleistocene glacial cycles hypothesized to suppress population isolation and allopatric speciation.     

Nonlethal sampling of DNA from critically endangered diving beetles (Coleoptera: Dytiscidae) using a single antenna

Nonlethal DNA sampling is highly desirable in molecular genetic studies of protected and endangered species. To develop a demonstrably nonlethal method of obtaining DNA from endangered diving beetles (Dytiscus sharpi sharpi Wehncke, Cybister lewisianus Sharp and Cybister brevis Aubé), we amputated the antennae of these endangered diving beetles and investigated the impact of the amputation on reproductive behaviors, egg‐laying and lifespan. Diving beetles with either one or no antennae copulated without delay and laid eggs, comparable to the pairs of intact beetles under breeding conditions. The lifespan of antennae‐amputated D. sharpi sharpi was the same as that of the intact beetles. A single antenna was sufficient to allow polymerase chain reaction (PCR) detection of a mitochondrial DNA gene, cytochrome‐c oxidase subunit I (COI), and the sequence of the COI gene could be determined directly. The PCR‐ready genomic DNA was available both in fresh antennae isolated from living beetles and in old antennae from whole beetles preserved for at least 5–6 years in pure ethanol. These results suggest that an antenna is a good sampling site for isolating genomic DNA from endangered diving beetles without sacrificing and disturbing reproductive behaviors such as mating and egg‐laying, or lifespan.     

Thermal tolerance and geographical range size in the Agabus brunneus group of European diving beetles (Coleoptera: Dytiscidae)

Aim Within clades, most taxa are rare, whilst few are common, a general pattern for which the causes remain poorly understood. Here we investigate the relationship between thermal performance (tolerance and acclimation ability) and the size of a species’ geographical range for an assemblage of four ecologically similar European diving beetles (the Agabus brunneus group) to examine whether thermal physiology relates to latitudinal range extent, and whether Brown’s hypothesis and the environmental variability hypothesis apply to these taxa. Location Europe. Methods In order to determine the species tolerances to either low or high temperatures we measured the lethal thermal limits of adults, previously acclimated at one of two temperatures, by means of thermal ramping experiments (± 1°C min^?1). These measures of upper and lower thermal tolerances (UTT and LTT respectively) were then used to estimate each species’ thermal tolerance range, as total thermal tolerance polygons and marginal UTT and LTT thermal polygons. Results Overall, widespread species have higher UTTs and lower LTTs than restricted ones. Mean upper lethal limits of the Agabus brunneus group (43 to 46°C), are similar to those of insects living at similar latitudes, whilst mean lower lethal limits (?6 to ?9°C) are relatively high, suggesting that this group is not particularly cold‐hardy compared with other mid‐temperate‐latitude insects. Widespread species possess the largest thermal tolerance ranges and have a relatively symmetrical tolerance to both high and low temperatures, when compared with range‐restricted relatives. Over the temperature range employed, adults did not acclimate to either high or low temperatures, contrasting with many insect groups, and suggesting that physiological plasticity has a limited role in shaping distribution. Main conclusions Absolute thermal niche appears to be a good predictor of latitudinal range, supporting both Brown’s hypothesis and the environmental variability hypothesis. Restricted‐range species may be more susceptible to the direct effect of climate change than widespread species, notwithstanding the possibility that even ‘thermally‐hardy’, widespread species may be influenced by the indirect effects of climate change such as reduction in habitat availability in Mediterranean areas.     

Early burst in body size evolution is uncoupled from species diversification in diving beetles (Dytiscidae)

Changes in morphology are often thought to be linked to changes in species diversification, which is expected to leave a signal of early burst (EB) in phenotypic traits. However, such signal is rarely recovered in empirical phylogenies, even for groups with well‐known adaptive radiation. Using a comprehensive phylogenetic approach in Dytiscidae, which harbours ~4,300 species with as much as 50‐fold variation in body size among them, we ask whether pattern of species diversification correlates with morphological evolution. Additionally, we test whether the large variation in body size is linked to habitat preference and whether the latter influences species turnover. We found, in sharp contrast to most animal groups, that Dytiscidae body size evolution follows an early‐burst model with subsequent high phylogenetic conservatism. However, we found no evidence for associated shifts in species diversification, which point to an uncoupled evolution of morphology and species diversification. We recovered the ancestral habitat of Dytiscidae as lentic (standing water), with many transitions to lotic habitat (running water) that are concomitant to a decrease in body size. Finally, we found no evidence for difference in net diversification rates between habitats nor difference in turnover in lentic and lotic species. This result, together with recent findings in dragonflies, contrasts with some theoretical expectations of the habitat stability hypothesis. Thus, a thorough reassessment of the impact of dispersal, gene flow and range size on the speciation process is needed to fully encompass the evolutionary consequences of the lentic–lotic divide for freshwater fauna.     

Recognition of a species-poor, geographically restricted but morphologically diverse Cape lineage of diving beetles (Coleoptera: Dytiscidae: Hyphydrini)

Aim To establish the phylogeny and geographical origin of the genera of the diving beetle tribe Hyphydrini in order to investigate the origin of differences in geographical range size, intrageneric species‐richness and morphological disparity. In particular, we tested the hypothesis that the geographically restricted, species‐poor and morphologically deviating genera found in the Cape Region of South Africa are a paraphyletic pool of ‘primitive’ Hyphydrini, from which the morphologically more uniform, species‐rich and geographically widespread genera have originated. Location Worldwide, with special reference to the Cape Region of South Africa. Methods We constructed a genus‐level molecular phylogeny of 10 of the 14 known genera of Hyphydrini, including the five endemic to the Cape Region, using sequences from four gene fragments (two mitochondrial, rrnL and cox1; and two nuclear, 18S rRNA and histone 3, c. 2200 bp). Phylogenies were built with Bayesian methods, and linearized using penalized likelihood. Morphological disparity was characterized by correspondence analysis of a data matrix of 21 binary characters. We compare morphological disparity among groups using distance to the global and local centroids and the total range of morphospace occupied. Geographical range was estimated using the number of 6° longitude × 8° latitude Universal Transverse Mercator squares known to contain any species of each genus. Results Hyphydrini is made up of four well supported clades of similar relative genetic divergence: (1) Hyphydrus (Old World plus Australasia, 133 species), (2) the five endemic genera of the Cape Region, sister to Hovahydrus (Madagascar) (10 species), (3) Desmopachria (America, 92 species), and (4) two Oriental genera (Microdytes and Allopachria, 68 species). The morphological disparity within the Cape Region lineage has apparently increased with time, with the two genera closest to the global centroid paraphyletic and basal with respect to the three more recent, morphologically deviating genera. Differences in the number of species between each of the four lineages were not significant. The correlation between the number of species in each lineage and geographical range extent was highly significant, with the low species number of the Cape Region (six) well within the 95% confidence interval of the regression. Main conclusions Contrary to expectations, the species‐poor, morphologically deviating endemic genera of the Cape Region are not a ‘primitive’ relictual pool from which the widespread, species‐rich and morphologically uniform genera have originated. The morphological disparity within the Cape lineage has increased with time, and the apparent lack of species‐level diversification disappears when species–area relationships are considered. A major unanswered question is why one of the four main lineages of Hyphydrini has remained restricted to a very reduced area (the Cape Region), but despite this evolved the highest degree of morphological diversity seen in the tribe.     

Mitochondrial DNA phylogeography and population history of Meladema diving beetles on the Atlantic Islands and in the Mediterranean basin (Coleoptera,Dytiscidae)

The phylogeny and population history of Meladema diving beetles (Coleoptera, Dytiscidae) were examined using mitochondrial DNA sequence from 16S ribosomal RNA and cytochrome oxidase I genes in 51 individuals from 22 populations of the three extant species (M. imbricata endemic to the western Canary Islands, M. lanio endemic to Madeira and M. coriacea widespread in the Western Mediterranean and on the western Canaries), using a combination of phylogenetic and nested clade analyses. Four main lineages are observed within Meladema, representing the three recognized species plus Corsican populations of M. coriacea. Phylogenetic analyses demonstrate the sister relationship of the two Atlantic Island taxa, and suggest the possible paraphyly of M. coriacea. A molecular clock approach reveals that speciation within the genus occurred in the Early Pleistocene, indicating that the Atlantic Island endemics are not Tertiary relict taxa as had been proposed previously. Our results point to past population bottlenecks in all four lineages, with recent (Late-Middle Pleistocene) range expansion in non-Corsican M. coriacea and M. imbricata. Within the Canary Islands, M. imbricata seems to have independently colonized La Gomera and La Palma from Tenerife (although a colonization of La Palma from La Gomera cannot be discarded), and M. coriacea has independently colonized Tenerife and Gran Canaria from separate mainland lineages. In the Mediterranean basin this species apparently colonized Corsica on a single occasion, relatively early in its evolutionary history (Early Pleistocene), and has colonized Mallorca recently on multiple occasions. On the only island where M. coriacea and M. imbricata are broadly sympatric (Tenerife), we report evidence of bidirectional hybridization between the two species.     

Fine-scale comparative phylogeography of a sympatric sister species triplet of subterranean diving beetles from a single calcrete aquifer in Western Australia

Calcrete aquifers in the arid Yilgarn region of central Western Australia are a biodiversity hotspot for stygofauna. A distinct pattern of interspecific size class variation among subterranean dytiscid beetle species has been observed in 29 of these aquifers where either two or three small, medium and/or large sympatric species are found that are in some cases sister species. We used a 3.5 km² grid of bores to sample dytiscids on a fine-scale and employed a comparative phylogeographical and population genetic approach to investigate the origins of a sympatric sister species triplet of diving beetles from a single aquifer. Mitochondrial DNA sequence data from the Cytochrome oxidase c subunit I gene revealed that all three species have high levels of haplotype diversity with ancient (∼1 million years ago) intra-specific coalescence of haplotypes, but low levels of nucleotide diversity. Population analyses provide evidence for multiple expansion events within each species. There was spatial heterogeneity in the distribution of genetic variation and abundance both within and among the three taxa. Population analyses revealed significant fine-scale differentiation with isolation by distance for Paroster macrosturtensis and P. mesosturtensis , but not the smallest species P. microsturtensis . Haplotype network analyses provided limited or no evidence for past population fragmentation within the large and small species, but substantial historical divergence was observed in P. mesosturtensis that was not spatially structured. A patchy population structure with contemporaneous and historical isolation by distance in the three species is likely to have been a significant isolating and diversifying force, preventing us from ruling out a potential role for allopatric divergence during speciation of this beetle sister triplet.     

Activity of free‐living subterranean blind mole rats Spalax galili (Rodentia: Spalacidae) in an area of supposed sympatric speciation

Subterranean rodents forage underground, which is energetically costly. Therefore, they can be expected to economize burrowing activity in response to food supply and soil characteristics. We analyzed the activity of radio‐tracked blind mole rats, Spalax galili, on a locality sharply subdivided into harder but relatively food‐rich, basaltic soil and softer, relatively food‐poor rendzina. It was recently proposed that the mole rats in this locality are undergoing sympatric ecological speciation. We predicted that mole rats from basaltic soil would be less active than those from rendzina as a result of the reduced need for burrowing to reach food. By contrast to our predictions, mole rats from basaltic soil were more frequently located outside the nest and observed pushing soil above ground. We suggest that this is a result of territorial behaviour due to high population density. All mole rats exhibited a unimodal daily activity pattern likely related to temperature. Large males had large but gradually decreasing home‐ranges, likely indicating the end of the mating season. We conclude that the ecological differences between the habitats cause behavioural differences in the mole rats, which indicates different selection pressures. The genetic divergence previously found between the populations might have arisen via density‐dependent selection.     

Paroster extraordinarius sp. nov., a new groundwater diving beetle from the Flinders Ranges, with notes on other diving beetles from gravels in South Australia (Coleoptera: Dytiscidae)

The first groundwater (stygobitic) diving beetle is reported from South Australia. Paroster extraordinarius sp. nov. (Dytiscidae: Hydroporini) is described and figured. Its morphology and mitochondrial DNA sequences place it in the hydroporine genus Paroster Sharp. Phylogenetic analysis shows that the new species is imbedded in a clade of stygobitic species from the Yilgarn area of Western Australia. The evolution of this species is discussed and compared with observations on the behaviour and distribution of other dytiscid beetles found in subterranean habitats in South Australia.     

Abundance and species richness patterns of diving beetles (Coleoptera, Dytiscidae) from exposed and protected sites in 98 northern Swedish lakes

Forty species of predaceous diving beetles (Coleoptera, Dytiscidae) were collected in sweepnet samples from 98 boreal lakes in northern Sweden. Samples from protected sites with vegetation had significantly more specimens and species than those from exposed sites without vegetation in the same lakes. No geographically based differences, e.g. latitudinal or in distance from the coast, were found. These gradients were 200 and 150 km long, respectively. Species' distribution in terms of occurence at number of sites was positively correlated with the mean abundance of the species. The relationship between species' abundance and body length was characterized by the lack of large, abundant species. Partial least square regressions on dytiscid abundance and species richness showed low predictive power of lake area, altitude and water chemistry. The seven environmental variables used explained at best 15.3 and 24.4% of the total variance in abundance and species richness, respectively. The results are compared to activity trap catches of dystiscids in lakes in an adjacent region. A majority of the species occured in both materials. However, species occuring in high proportion in one of the materials, were rare in the other material. The mean body length of the species caught more efficiently with traps was not larger than that of those overpresented in net sampling. Based on this study and the available literature data, the regional species pool of boreal lake dytiscids is estimated to 30–40 species. It is still an open question if lake assemblages are markedly poorer than those found in the development of vegetation, whereas the impact of water chemistry is small.     

Species richness patterns of obligate subterranean beetles (Insecta: Coleoptera) in a global biodiversity hotspot – effect of scale and sampling intensity

We studied species richness patterns of obligate subterranean (troglobiotic) beetles in the Dinaric karst of the western Balkans, using five grid sizes with cells of 80 × 80, 40 × 40, 20 × 20, 10 × 10, and 5 × 5 km. The same two hotspots could be recognized at all scales, although details differed. Differences in sampling intensity were not sufficient to explain these patterns. Correlations between number of species and number of sampled localities increased with increasing cell size. Additional species are expected to be found in the region, as indicated by jackknife 1, jackknife 2, Chao2, bootstrap, and incidence‐based coverage (ICE) species richness estimators. All estimates increased with increasing cell size, except Chao2, with the lowest prediction at the intermediate 20 × 20 km cell size. Jackknife 2 and ICE gave highest estimates and jackknife 1 and bootstrap the lowest. Jackknife 1 and bootstrap estimates changed least with cell size, while the number of single cell species increased. In the highly endemic subterranean fauna with many rare species, bootstrap may be most appropriate to consider. Positive autocorrelation of species numbers was highest at 20 × 20 km scale, so we used this cell size for further analyses. At this scale we added 137 localities with less positional accuracy to 1572 previously considered, and increased 254 troglobiotic species considered to 276. Previously discovered hotspots and their positions did not change, except for a new species‐rich cell which appeared in the south‐eastern region. There are two centres of troglobiotic species richness in the Dinaric karst. The one in the north‐west exhibited high species richness of Trechinae (Carabidae), while in the south‐east, the Leptodirinae (Cholevidae) were much more diverse. These centres of species richness should serve as the starting point for establishing a conservation network of important subterranean areas in Dinaric karst.     

A south-to-north biogeographic hypothesis for Andean speciation: evidence from the lizard genus Proctoporus (Reptilia, Gymnophthalmidae)

Aim The lizard genus Proctoporus Tschudi, 1845 was used as a model to test the South‐to‐North Speciation Hypothesis (SNSH) for species groups occurring in the Andes Mountains of South America. This hypothesis proposes that speciation of high Andean taxa followed a south‐to‐north pattern, generally coinciding with the progression of final uplift of the Andes. According to SNSH, a phylogenetic hypothesis of relationships of a taxonomic group occurring in the high Andes would show a branching pattern in which the southernmost species diverged first, followed by the more northern species, and so on in a northerly pattern. Location The central and northern Andes Mountains in South America. Methods A phylogenetic hypothesis was reconstructed for all species of the lizard genus Proctoporus by examining the external morphology of 341 individuals. This phylogeny was then examined to determine monophyly of the genus, distribution patterns of species groups, and congruence with SNSH. Results The genus Proctoporus did appear to be monophyletic and, therefore, it was valid to use this group to assess SNSH. The southernmost species were found to be the most basal, which was consistent with SNSH. The species occurring in the northern Andes did not exactly match the SNSH prediction. The Venezuelan and Trinidadian species did appear to be highly derived, as predicted by the hypothesis, but the Ecuadorian and Colombian species did not form a particular pattern in relation to the hypothesis. Main conclusions The SNSH does appear to have predictive power with regard to large‐scale distribution patterns. The finer‐scale patterns of speciation in the Andes, however, appear to be a more complex phenomenon that cannot be fully explained by a simple hypothesis. It is important to have a testable hypothesis in hand with which to compare data from disparate species groups. The incorporation of phylogenetic data of other high Andean taxa with similar distribution patterns is necessary to determine the full utility of SNSH in explaining evolutionary patterns in the Andes of South America.     

Molecular inference of a Late Pleistocene diversification shift in Nigella s. lat. (Ranunculaceae) resulting from increased speciation in the Aegean archipelago

Aim  To infer the temporal course and geographical mode of speciation in Mediterranean/Southwest Asian Nigella s. lat.
Location  Mediterranean Basin, Aegean archipelago.
Methods  Phylogenies for Nigella L. and Garidella L. (=  Nigella s. lat.) were obtained from maximum-likelihood analyses of internal transcribed spacer (ITS) sequences. Diversification through time was analysed by log lineages-through-time (LTT) plots and survival analyses. Relative node age estimates were regressed against the degree of sympatry between sister clades to infer the predominant mode of geographical speciation in Nigella s. lat.
Results  The Late Pleistocene radiation of the Nigella arvensis complex in the Aegean region caused a significant departure from a stochastic speciation/extinction process of diversification during the evolution of Nigella s. lat., a lineage of (at least) Late Miocene origin. Speciation within Nigella s. lat. predominantly took place in allopatry.
Main conclusions  No significant effect on diversification rate was found regarding the establishment of a Mediterranean-type climate, or the onset of the Quaternary climatic oscillations. Rather, the accelerated rate of speciation in the N. arvensis complex is plausibly related to increased opportunities for allopatric speciation afforded by the (palaeo)geographical complexity of the Aegean archipelago combined with Late Pleistocene changes in climate and sea level. The evolution of self-pollination and associated changes in habitat preference and flowering time further augmented speciation and niche differentiation within the complex, but these changes did not act as the primary promoters of the radiation process.     

Recent origin,active speciation and dispersal for the lichen genus Nephroma (Peltigerales) in Macaronesia

Aim We reconstructed the phylogeny of the lichen genus Nephroma (Peltigerales) to assess the relationships of species endemic to Macaronesia. We estimated dates of divergences to test the hypothesis that the species arose in Macaronesia (neo‐endemism) versus the oceanic archipelagos serving as refugia for formerly widespread taxa (palaeo‐endemism). Location Cosmopolitan with a special focus on the archipelagos of the Azores, Madeira and the Canary Islands. Methods DNA sequences were obtained from 18 species for three loci and analysed using maximum parsimony, maximum likelihood and Bayesian inferences. Divergence dates were estimated for the internal transcribed spacer (ITS)‐based phylogeny using a relaxed molecular clock. Reconstruction of the ancestral geographical range was conducted using the Bayesian 50% majority rule consensus tree under a parsimony method. Results The backbone phylogenetic tree was fully supported, with Nephroma plumbeum as sister to all other species. Four strongly supported clades were detected: the Nephroma helveticum, the N. bellum, the N. laevigatum and the N. parile clades. The latter two share a common ancestor and each includes a widespread Holarctic species (N. laevigatum and N. parile, respectively) and all species endemic to Macaronesia. The data suggest a neo‐endemic origin of Macaronesian taxa, a recent range expansion from Macaronesia of both widespread species, a range expansion limited to the Mediteranean Basin and south‐western Europe for another taxon, and a long dispersal event that resulted in a speciation event in the western parts of North America. Main conclusions The Macaronesian endemic species belong to two sister clades and originated from a most recent common ancestor (MRCA) shared with one widely distributed taxon, either N. parile or N. laevigatum. Estimates of the mean divergence dates suggest that the endemics originated in the archipelagos after the rise of the volcanic islands, along with the ancestor to the now widespread species, which probably expanded their range beyond Macaronesia via long‐distance dispersal. This study provides the first phylogenetic evidence of Macaronesian neo‐endemism in lichenized fungi and provides support for the hypothesis that oceanic islands may serve as a source for the colonization of continents. However, further data are needed to properly assess the alternative hypothesis, namely colonization from western North America.     

Evidence for parallel ecological speciation in scincid lizards of the Eumeces skiltonianus species group (Squamata: Scincidae)

We identify instances of parallel morphological evolution in North American scincid lizards of the Eumeces skiltonianus species group and provide evidence that this system is consistent with a model of ecological speciation. The group consists of three putative species divided among two morphotypes, the small-bodied and striped E. skiltonianus and E. lagunensis versus the large-bodied and typically uniform-colored E. gilberti. Members of the group pass through markedly similar phenotypic stages during early development, but differ with respect to where terminal morphology occurs along the developmental sequence. The morphotypes also differ in habitat preference, with the large-bodied gilberti form generally inhabiting lower elevations and drier environments than the smaller, striped morphs. We inferred the phylogenetic relationships of 53 skiltonianus group populations using mtDNA sequence data from the ND4 protein-coding gene and three flanking tRNAs (900 bp total). Sampling encompassed nearly the entire geographic range of the group, and all currently recognized species and subspecies were included. Our results provide strong evidence for parallel origins of three clades characterized by the gilberti morphotype, two of which are nested within the more geographically widespread E. skiltonianus. Eumeces lagunensis was also nested among populations of E. skiltonianus. Comparative analyses using independent contrasts show that evolutionary changes in body size are correlated with differences in adult color pattern. The independently derived association of gilberti morphology with warm, arid environments suggests that phenotypic divergence is the result of adaptation to contrasting selection regimes. We provide evidence that body size was likely the target of natural selection, and that divergences in color pattern and mate recognition are probable secondary consequences of evolving large body size.     

Ecological speciation in anemone‐associated snapping shrimps (Alpheus armatus species complex)

Divergent natural selection driven by competition for limited resources can promote speciation, even in the presence of gene flow. Reproductive isolation is more likely to result from divergent selection when the partitioned resource is closely linked to mating. Obligate symbiosis and host fidelity (mating on or near the host) can provide this link, creating ideal conditions for speciation in the absence of physical barriers to dispersal. Symbiotic organisms often experience competition for hosts, and host fidelity ensures that divergent selection for a specific host or host habitat can lead to speciation and strengthen pre‐existing reproductive barriers. Here, we present evidence that diversification of a sympatric species complex occurred despite the potential for gene flow and that partitioning of host resources (both by species and by host habitat) has contributed to this diversification. Four species of snapping shrimps (Alpheus armatus, A. immaculatus, A. polystictus and A. roquensis) are distributed mainly sympatrically in the Caribbean, while the fifth species (A. rudolphi) is restricted to Brazil. All five species are obligate commensals of sea anemones with a high degree of fidelity and ecological specificity for host species and habitat. We analysed sequence data from 10 nuclear genes and the mitochondrial COI gene in 11–16 individuals from each of the Caribbean taxa and from the only available specimen of the Brazilian taxon. Phylogenetic analyses support morphology‐based species assignments and a well‐supported Caribbean clade. The Brazilian A. rudolphi is recovered as an outgroup to the Caribbean taxa. Isolation–migration coalescent analysis provides evidence for historical gene flow among sympatric sister species. Our data suggest that both selection for a novel host and selection for host microhabitat may have promoted diversification of this complex despite gene flow.     

Molecular phylogenetics of Atlantic Shield Platynectes diving beetles (Coleoptera: Dytiscidae): a first glance at the evolution of the genus in the Amazon Basin

Neotropical diving beetles of the genus Platynectes are distributed across Central America, the Andes and different Precambrian shields in the Amazon Basin. Species from the northern Guiana Shield form a monophyletic clade, yet the phylogenetic relationships of the eastern Atlantic Shield species remain unknown. Here, we augmented an existing molecular dataset with a species from the Atlantic Shield that was not previously sampled. We reconstructed the phylogenetic relationships and estimated divergence times to understand the evolution of lineages dwelling in this region. The newly sampled specimens from the Atlantic Shield are recovered as sister taxa to Guiana Shield species. The dating analyses suggest a split between these two lineages in the late Oligocene to mid-Miocene, contemporary with the Miocenic geological remodeling of the Amazon Basin. Additional sampling in the Atlantic and Central Brazilian Shields will be determinant to test the monophyly of Platynectes species distributed in these ancient shields, and to fully understand the biogeographical history of diving beetles in the Amazon Basin.     

Niche evolution and diversification in a Neotropical radiation of birds (Aves: Furnariidae)

Rapid diversification may be caused by ecological adaptive radiation via niche divergence. In this model, speciation is coupled with niche divergence and lineage diversification is predicted to be correlated with rates of niche evolution. Studies of the role of niche evolution in diversification have generally focused on ecomorphological diversification but climatic‐niche evolution may also be important. We tested these alternatives using a phylogeny of 298 species of ovenbirds (Aves: Furnariidae). We found that within Furnariidae, variation in species richness and diversification rates of subclades were best predicted by rate of climatic‐niche evolution than ecomorphological evolution. Although both are clearly important, univariate regression and multivariate model averaging more consistently supported the climatic‐niche as the best predictor of lineage diversification. Our study adds to the growing body of evidence, suggesting that climatic‐niche divergence may be an important driver of rapid diversification in addition to ecomorphological evolution. However, this pattern may depend on the phylogenetic scale at which rate heterogeneity is examined.     

Evidence for ecological speciation via a host shift in the holly leaf miner,Phytomyza glabricola (Diptera: Agromyzidae)

Evolutionary radiations have been well documented in plants and insects, and natural selection may often underly these radiations. If radiations are adaptive, the diversity of species could be due to ecological speciation in these lineages. Agromyzid flies exhibit patterns of repeated host‐associated radiations. We investigated whether host‐associated population divergence and evidence of divergent selection exist in the leaf miner Phytomyza glabricola on its sympatric host plants, the holly species, Ilex coriacea and I. glabra. Using AFLPs and nuclear sequence data, we found substantial genetic divergence between host‐associated populations of these flies throughout their geographic range. Genome scans using the AFLP data identified 13 loci under divergent selection, consistent with processes of ecological speciation. EF‐1α data suggest that I. glabra is the original host of P. glabricola and that I. coriacea is the novel host, but the AFLP data are ambiguous with regard to directionality of the host shift.