Vagility across Vanessa (Lepidoptera: Nymphalidae): mobility in butterfly species does not inhibit the formation and persistence of isolated sister taxa

Allopatric speciation is thought to occur in the absence of gene flow, thereby suggesting that widespread vagile species might be less likely to generate restricted sister taxa because of a lack of isolation. The butterfly genus Vanessa provides an ideal test of this concept, as it contains some of the most cosmopolitan and vagile species of butterflies on the planet, as well as some highly restricted taxa. Given the age of these groups, this arrangement offers a special opportunity to examine the relationship between vagility and phylogeny in generating novel taxa; specifically, does the vagility of some lineages impede allopatric speciation, leaving restricted clades more speciose? A phylogenetic hypothesis is proposed for all species belonging to the butterfly genus Vanessa based on DNA sequences from one mitochondrial and eight nuclear gene regions. The resulting topology shows very little conflict among gene regions, with five well‐supported clades corresponding to morphologically consistent species groups. The data very strongly indicate a polyphyletic genus Antanartia, and thus to preserve monophyly two species previously assigned to Antanartia are transferred to Vanessa, Vanessa hippomene comb.n. and Vanessa dimorphica comb.n. , resulting in a total of 22 species placed in Vanessa. A biogeographical analysis shows that in many cases the most geographically restricted species are sister to geographically widespread species, suggesting dispersal and allopatric speciation. Surprisingly, in almost all cases the divergences between widespread and restricted species are quite old (>5 Ma), suggesting long‐term isolation and stability of both vagile and sedentary species, despite the high (even intercontinental) vagility of many extant species and, by extension, ancestral species. The biogeography of Vanessa suggests that species vagility and allopatry do not fully explain the forces governing cladogenesis in this remarkable genus.     

Phylogenetics and biogeography of the two‐wing flyingfish (Exocoetidae: Exocoetus)

Two‐wing flyingfish (Exocoetus spp.) are widely distributed, epipelagic, mid‐trophic organisms that feed on zooplankton and are preyed upon by numerous predators (e.g., tunas, dolphinfish, tropical seabirds), yet an understanding of their speciation and systematics is lacking. As a model of epipelagic fish speciation and to investigate mechanisms that increase biodiversity, we studied the phylogeny and biogeography of Exocoetus, a highly abundant holoepipelagic fish taxon of the tropical open ocean. Morphological and molecular data were used to evaluate the phylogenetic relationships, species boundaries, and biogeographic patterns of the five putative Exocoetus species. We show that the most widespread species (E. volitans) is sister to all other species, and we find no evidence for cryptic species in this taxon. Sister relationship between E. monocirrhus (Indo‐Pacific) and E. obtusirostris (Atlantic) indicates the Isthmus of Panama and/or Benguela Barrier may have played a role in their divergence via allopatric speciation. The sister species E. peruvianus and E. gibbosus are found in different regions of the Pacific Ocean; however, our molecular results do not show a clear distinction between these species, indicating recent divergence or ongoing gene flow. Overall, our phylogeny reveals that the most spatially restricted species are more recently derived, suggesting that allopatric barriers may drive speciation, but subsequent dispersal and range expansion may affect the distributions of species.     

Phylogenetic systematics and historical biogeography of the Neotropical electric fish Gymnotus (Teleostei: Gymnotidae)

Phylogenetic interrelationships of the Neotropical electric fish genus Gymnotus are documented from comparative study of phenotypic data. A data matrix was compiled of 113 phenotypic characters for 40 taxa, including 31 recognized Gymnotus species, six allopatric populations of G. carapo, two allopatric populations of G. coropinae, and three gymno‐tiform outgroups. MP analysis yielded 15 trees of equal length, the strict consensus of which is presented as a working hypothesis of Gymnotus interrelationships. Diagnoses are presented for 26 clades, including three species groups; the G. cylindricus group with two species restricted to Middle America, the G. pantherinus group with 12 species in South America, and the G. carapo group with 16 species in South America. The basal division of Gymnotus is between clades endemic to Middle and South America. Both the G. pantherinus and G. carapo groups include trans‐Andean sister‐taxon pairs, suggesting a minimum date for the origins of these groups in the late Middle Miocene (c. 12 Ma.). The geographically widespread species G. carapo is paraphyletic. Analysis of character state evolution shows characters of external morphology are more phylogenetically plastic and provide more phylogenetic information in recent branches than do characters of internal morphology, which themselves provide the more information in deeper branches. Nine regional species assemblages of Gymnotus are recognized, none of which is monophyletic. There are at least two independent origins of Gymnotus species in sediment rich, high conductivity, perennially hypoxic whitewater floodplains (varzea´) derived from an ancestral condition of being restricted to low conductivity non‐floodplain (terra firme) black and clearwater rivers and streams. These phylogenetic, biogeographic and ecological patterns suggest a lengthy and complex history involving numerous instances of speciation, extinction, migration and coexistence in sympatry. Evolution in Gymnotus has been a continent‐wide phenomenon; i.e. Amazonian species richness is not a consequence of strictly Amazonian processes. These patterns are similar to those of other highly diverse groups of Neotropical fishes and do not resemble those of monophyletic, rapidly generated species flocks.     

Variation in hostplant relations and courtship signals of weed-associated populations of the brown planthopper, Nilaparvata lugens (Stål), from Australia and Asia: a test of the recognition species concept

Populations of the morphological species, Nilaparvata lugens (Stål), were found to breed and feed on the grass, Leersia hexandra Schwartz, at six sites in Queensland, Australia. They differ from sympatric rice-feeding populations in characters of pulse repetition frequencies of male and female acoustic courtship signals. The two host-derived populations hybridize freely in the laboratory, but in mate choice experiments show very significant preferences for homogametic matings. No indication of field hybridization has been found, so that the two morphologically inseparable populations represent sympatric biological species in Australia.
Populations from L. hexandra are also reported from four localities in Sri Lanka and one in Orissa, India. These resemble previously studied populations from the Philippines. They differ significantly in courtship call characters, both from sympatric rice-associated populations and from allopatric Leersia -associated populations from Australia.
The geographical variation reported for acoustic signals is not consistent with Paterson's recognition concept of species, but may be interpreted in terms of theories of allopatric speciation involving sexual selection for mate recognition signals.     

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.     

The role of head shape and trophic variation in the diversification of the genus Herichthys in sympatry and allopatry

In the present study we evaluated the putative cases of sympatric speciation in the genus Herichthys by studying the variation in head shape using principal component analysis, phylomorphospace and reconstructions of the ancestral states of feeding preferences. Herichthys includes both allopatric and sympatric sister species, as well as sympatric unrelated species and thus offers great potential for evolutionary studies of putatively sympatric speciation. Herichthys is the northernmost group of cichlids in America and one of the most ecologically disparate genera within Middle American cichlids. Fifteen anatomical points were recorded on the heads of 293 specimens of the 11 species recognized within the genus. The results show that in spite of having wide variation in consumed diets, most species of Herichthys are close in morphospace. However, morphological variation was great among the two pairs of sympatric sister species in agreement with the suggested sympatric model of speciation.     

Genetic and chaetal variation in Nais worms (Annelida,Clitellata, Naididae)

The genus Nais is a group of oligochaetous clitellates, common in eutrophic freshwater habitats. About 30 species are described. Species identification is based primarily on chaetal characters, which are often subtle, inconsistent, and even overlapping between nominal species. We investigated the correlation between genetic variation and chaetal morphology in this genus. Eighty‐one individuals from Europe, North America, and China were included in the study. Seventy‐five of these were preserved as vouchers. They were scrutinized with regard to chaetal morphology, and ten different morphotypes were identified. Three molecular markers, two mitochondrial (the COI gene and 16S rDNA) and one nuclear (the ITS region), were used to establish the genetic lineages in the material. Genetic variation was found to be largely congruent with chaetal character patterns. However, at least nine separately evolving lineages (all supported by mitochondrial as well as nuclear data) correspond to at most six nominal species. Four morphotypes/lineages are recognized as Nais barbata, Nais christinae, Nais elinguis, and Nais stolci, respectively, whereas five, or possibly more, lineages represent a morphological continuum covering the variation of the Nais communis/variabilis complex. Thus, cryptic speciation is revealed. Our results indicate that a taxonomic revision of the genus will be needed in the future.     

Molecular phylogenetics of the hummingbird genus Coeligena

Advances in the understanding of biological radiations along tropical mountains depend on the knowledge of phylogenetic relationships among species. Here we present a species-level molecular phylogeny based on a multilocus dataset for the Andean hummingbird genus Coeligena. We compare this phylogeny to previous hypotheses of evolutionary relationships and use it as a framework to understand patterns in the evolution of sexual dichromatism and in the biogeography of speciation within the Andes. Previous phylogenetic hypotheses based mostly on similarities in coloration conflicted with our molecular phylogeny, emphasizing the unreliability of color characters for phylogenetic inference. Two major clades, one monochromatic and the other dichromatic, were found in Coeligena. Closely related species were either allopatric or parapatric on opposite mountain slopes. No sister lineages replaced each other along an elevational gradient. Our results indicate the importance of geographic isolation for speciation in this group and the potential interaction between isolation and sexual selection to promote diversification.     

Local endemism and within‐island diversification of shrews illustrate the importance of speciation in building Sundaland mammal diversity

Island systems are important models for evolutionary biology because they provide convenient, discrete biogeographic units of study. Continental islands with a history of intermittent dry land connections confound the discrete definitions of islands and have led zoologists to predict (i) little differentiation of terrestrial organisms among continental shelf islands and (ii) extinction, rather than speciation, to be the main cause of differences in community composition among islands. However, few continental island systems have been subjected to well‐sampled phylogeographic studies, leaving these biogeographic assumptions of connectivity largely untested. We analysed nine unlinked loci from shrews of the genus Crocidura from seven mountains and two lowland localities on the Sundaic continental shelf islands of Sumatra and Java. Coalescent species delimitation strongly supported all currently recognized Crocidura species from Sumatra (six species) and Java (five species), as well as one undescribed species endemic to each island. We find that nearly all species of Crocidura in the region are endemic to a single island and several of these have their closest relative(s) on the same island. Intra‐island genetic divergence among allopatric, conspecific populations is often substantial, perhaps indicating species‐level diversity remains underestimated. One recent (Pleistocene) speciation event generated two morphologically distinct, syntopic species on Java, further highlighting the prevalence of within‐island diversification. Our results suggest that both between‐ and within‐island speciation processes generated local endemism in Sundaland, supplementing the traditional view that the region's fauna is relictual and primarily governed by extinction.     

Geographic variation and divergence of songs in the Olive Sparrow species complex

Phenotypic traits such as songs are important in species recognition. Variation in acoustic traits can form barriers to gene flow and promote speciation. Therefore, understanding song divergence is crucial in groups with controversial taxonomy such as Olive Sparrows (Arremonops rufivirgatus), a widespread Neotropical species of songbird with multiple allopatric populations. Taxonomic authorities disagree on the number of Olive Sparrow subspecies, placing them into either two or three main groups. These groups may represent separate species based on morphological traits, but trait divergence within the complex has not been examined. We studied geographic variation in the characteristics of the songs of Olive Sparrows at two geographical levels: among three proposed groups and among five allopatric populations. In a second analysis, we evaluated the strength of acoustic divergence within the complex by comparing acoustic distances among groups and allopatric populations of Olive Sparrows with the acoustic distance among three recognized species in the genus Arremonops. We analyzed 802 songs from 174 individuals across 81 locations and measured 12 variables to describe the fine structural characteristics of the songs of Olive Sparrows, Green-backed Sparrows (A. chloronotus), Black-striped Sparrows (A. conirostris), and Tocuyo Sparrows (A. tocuyensis). We found significant acoustic variation in the Olive Sparrow complex at both geographical levels. Our divergence analysis also revealed that vocal divergence within the complex is similar to or greater than that found between recognized species in the genus. Together, these results suggest that acoustic diversity within the Olive Sparrow complex probably originated by isolation in tandem with selective and/or non-selective factors.     

Inferring the mode of speciation in Indo-West Pacific Conus (Gastropoda: Conidae)

Aim This study aims to initially explore the mode of speciation in Indo‐West Pacific Conus. Location The Indo‐West Pacific island arc, Indian and Pacific Oceans. Methods Relating evolutionary divergence in a molecular phylogeny [T.F. Duda & S.R. Palumbi (1999) Proceedings of the National Academy of Science USA, 96 , 10272] using node height with modern range extents as a possible measure of allopatric or sympatric speciation following that of T.G. Barraclough, A.P. Vogler & P.H. Harvey [(1999) Evolution of Biological Diversity. Oxford University Press, Oxford] models of sympatric and allopatric speciation. Results The analysis seems to indicate that the relationship of sympatry with node height is not informative. Species that have diverged quite recently show 100% sympatry with the sister species. A clearer signal of recent allopatric speciation is observed in species whose distribution is at the edge of the Indian and Pacific Ocean basins. In the widely distributed Conus ebraeus clade, the relationships of node heights and range extents of the member species support a key prediction of sympatric speciation. In highly ecologically specialized species, there is a smaller degree of sympatry than those species that are less specialized. Main conclusions The modes of speciation models presented in this study are not informative. This suggests that there had been large and possibly rapid changes in range size after speciation in the various clades. This could have been due to the fact that the wide dispersal life‐history strategy in the genus had been largely conserved in Conus evolution. There is evidence of sympatric and parapatric speciation in one Conus clade. Overall, the patterns of phylogeny and range distribution when related to the timing of speciation lend circumstantial support to a Neogene centre of origin hypothesis but not to speciation on the Pacific Plate. Speciation is likely to have been associated with the Tethys Sea closure event, with rapid speciation occurring after closure.     

Phylogeny and biogeography Eupholidoptera Mařan (Orthoptera,Tettigoniidae): morphological speciation in correlation with the geographical evolution of the eastern Mediterranean

Recently, the systematics and biogeography of the Mediterranean biota have received much attention. This paper deals with Eupholidoptera Ma?an, a Mediterranean lineage of Tettigoniidae. The genus is restricted to the northern and eastern basin of the Mediterranean, with a significant number of species found on the Aegean islands. To produce a phylogeny and use it to make assumptions about the historical biogeography of Eupholidoptera, material of 46 species from several collections was studied. A phylogenetic analysis based mainly on morphological characters suggested two lineages in the genus: the E. chabrieri and the E. prasina groups. Based on the consistency between historical geographical events and branching events on the phylogenetic tree, Eupholidoptera is assumed to have evolved from an ancestor present in the Aegeid plate in the Mid‐Miocene. The division of the Aegeid plate into Anatolia and Greece in the Tortonian, the reoccurrence of terrestrial corridors between these mainlands in the Messinian, the regression of the Aegean area in the Pliocene and sea level changes in the Pleistocene are assumed to have been the main palaeogeographical events directing speciation in Eupholidoptera. As most of the species are allopatric, vicariance is suggested to be the main pattern. By combining the nature of the characters used in the phylogenetic analysis, the phylogenetic tree produced and the biogeographical assumptions, four tentative conclusions can be made: (i) radiation in the genus is a result of divergence in morphology; (ii) because the main character source is male genitalia, there has possibly been intensive sexual selection, which leads to morphological speciation; (iii) as the difference in temporal parameters of the song is prominent in sympatric/parapatric species pairs only, co‐occurrence is suggested to be the main reason driving divergence in the song; (iv) there seems to be a negative correlation between the size of the distribution range and the evolutionary rate in speciation; this may be the reason why the E. prasina group (restricted to a small part of the range of the genus) is more diverse than the E. chabrieri group, which is distributed over the entire range.     

Ecological divergence and speciation between lemur (Eulemur) sister species in Madagascar

Understanding ecological niche evolution over evolutionary timescales is crucial to elucidating the biogeographic history of organisms. Here, we used, for the first time, climate‐based ecological niche models (ENMs) to test hypotheses about ecological divergence and speciation processes between sister species pairs of lemurs (genus Eulemur) in Madagascar. We produced ENMs for eight species, all of which had significant validation support. Among the four sister species pairs, we found nonequivalent niches between sisters, varying degrees of niche overlap in ecological and geographic space, and support for multiple divergence processes. Specifically, three sister‐pair comparisons supported the null model that niches are no more divergent than the available background region. These findings are consistent with an allopatric speciation model, and for two sister pairs (E. collaris–E. cinereiceps and E. rufus–E. rufifrons), a riverine barrier has been previously proposed for driving allopatric speciation. However, for the fourth sister pair E. flavifrons–E. macaco, we found support for significant niche divergence, and consistent with their parapatric distribution on an ecotone and the lack of obvious geographic barriers, these findings most strongly support a parapatric model of speciation. These analyses thus suggest that various speciation processes have led to diversification among closely related Eulemur species.     

Speciation and dietary specialization in Drupa,a genus of predatory marine snails (Gastropoda: Muricidae)

Claremont, M., Reid, D.G. & Williams, S.T. (2012) Speciation and dietary specialization in Drupa, a genus of predatory marine snails (Gastropoda: Muricidae). —Zoologica Scripta, 41, 137–149. We test the competing predictions of allopatric speciation and of ecological speciation by dietary specialization in Drupa, an Indo‐Pacific genus of carnivorous marine gastropods in the family Muricidae. We use a well‐resolved molecular phylogeny (reconstructed from one nuclear and two mitochondrial genes) to show the validity of the traditional species D. elegans, D. rubusidaeus, D. clathrata, D. morum and D. speciosa.‘Drupa ricinus’ is shown to consist of three species: D. ricinus s. s., D. albolabris and a new species, possibly endemic to Japan. ‘Purpura’aperta is transferred to Drupa. Despite potential widespread dispersal and a high degree of range overlap among sister species, range sizes between sister species are highly asymmetric, suggesting that speciation has been predominately peripatric. The exception is the sister pair D. ricinus s. s. and D. albolabris, which have symmetric range sizes and are sympatric over broad Indo‐Pacific ranges. Such symmetry and extensive sympatry are contrary to the predictions of the (peripatric) allopatric model of speciation. Nevertheless, contrary to the predictions of an ecological speciation model based upon dietary specialization, broad dietary range appears to be identical between the species. Small differences in microhabitat preferences (or hypothetical dietary specialization at a fine taxonomic scale) may have been significant in the speciation process or, if initial divergence was allopatric, in permitting subsequent sympatry. Broad dietary shifts appear to have accompanied more ancient divergences within the genus Drupa.     

Allopatry and overlap in a clade of snails from mangroves and mud flats in the Indo‐West Pacific and Mediterranean (Gastropoda: Potamididae: Cerithideopsilla)

Cerithideopsilla is a genus of potamidid snails found in high abundance on sedimentary intertidal flats and beneath mangrove trees on continental shores in the tropical and subtropical Indo‐West Pacific region and Mediterranean Sea. Taxonomic revisions have recognized four species, but recent molecular studies have hinted at a higher diversity. Here, we analyse 377 individuals sampled from across the known range and use a combination of molecular phylogenetic (mitochondrial COI and 16S rRNA, and nuclear 28S rRNA genes), statistical (generalized mixed Yule‐coalescent GMYC method) and morphological (shell form) criteria to delimit 16 species. These form four species groups, corresponding with the traditionally recognized species C. alata, C. ‘djadjariensis’ (for which the valid name is C. incisa), C. cingulata and C. conica. Distribution maps were compiled using museum specimens identified by diagnostic shell characters. In combination with the molecular phylogenetic trees, these suggest an allopatric speciation mode, with diversification centred on the East Asian coastline and northern Australia, and a pronounced gap in the ‘eastern Indonesian corridor’, an area of low oceanic productivity. There is, however, frequently geographical overlap between sister species and we suggest from several sources of evidence (e.g. presence of C. conica in isolated saline lakes 900 km from the sea) that post‐speciation transport by migratory birds has occurred. Nine of the 16 species occur between the Gulf of Tonkin and Hong Kong, so southern China is significant for both the evolution and conservation of Cerithideopsilla species. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114 , 212–228.     

Mosaics in the mangroves: allopatric diversification of tree‐climbing mudwhelks (Gastropoda: Potamididae: Cerithidea) in the Indo‐West Pacific

The Indo‐Australian Archipelago (IAA) is the richest area of biodiversity in the marine realm, yet the processes that generate and maintain this diversity are poorly understood and have hardly been studied in the mangrove biotope. Cerithidea is a genus of marine and brackish‐water snails restricted to mangrove habitats in the Indo‐West Pacific, and its species are believed to have a short pelagic larval life. Using molecular and morphological techniques, we demonstrate the existence of 15 species, reconstruct their phylogeny and plot their geographical ranges. Sister species show a pattern of narrowly allopatric ranges across the IAA, with overlap only between clades that show evidence of ecological differentiation. These allopatric mosaic distributions suggest that speciation may have been driven by isolation during low sea‐level stands, during episodes preceding the Plio‐Pleistocene glaciations. The Makassar Strait forms a biogeographical barrier hindering eastward dispersal, corresponding to part of Wallace's Line in the terrestrial realm. Areas of maximum diversity of mangrove plants and their associated molluscs do not coincide closely. © 2013 The Natural History Museum. Biological Journal of the Linnean Society © 2013 The Linnean Society of London, 2013, 110 , 564–580.     

An integrative approach to reveal speciation and species richness in the genus Diasporus (Amphibia: Anura: Eleutherodactylidae) in eastern Panama

We have applied an integrative taxonomic approach, including bioacoustics, ecology, morphology, and molecular genetics (barcoding and phylogeography), to explore species richness in the genus Diasporus in eastern Panama, from where only Diasporus quidditus (Lynch, 2001) was previously known. During fieldwork in eastern Panama in 2011 and 2012 we found six additional species, four of which we are describing here as new to science, plus two species that are new for this region. We have evaluated the presence of Diasporus diastema (Cope, 1875) in eastern Panama by comparing morphological, genetic, and bioacoustic characters of specimens from near the type locality in central Panama with specimens from eastern Panama. We further describe and compare male advertisement calls of most Diasporus species. The phylogeographic analysis suggests the allopatric speciation of Diasporus species in eastern Panama following the completion of the Panamanian isthmus in the middle Miocene. Subsequent geological events concur with the vicariant evolution of different lineages in situ, suggesting eastern Panama to be a centre of endemism for this group of frogs. We present an integrative analysis of the species from eastern Panama and include an identification key for all species of the genus.     

Increased floral divergence in sympatric monkeyflowers

Sympatric sister species are predicted to have greater divergence in reproductive traits than allopatric sister species, especially if mating system shifts, such as the evolution of self-fertilization, are more likely to originate within the geographic range of the outcrossing ancestor. We present evidence that supports this expectation-sympatric sister species in the monkeyflower genus, Mimulus, exhibit greater divergence in flower size than allopatric sister species. Additionally, we find that sympatric sister species are more likely to have one species with anthers that overtop their stigmas than allopatric sister species, suggesting that the evolution of automatic self-pollination may contribute to this pattern. Potential mechanisms underlying this pattern include reinforcement and a stepping stone model of parapatric speciation.