The evolution of sexual and parthenogenetic Warramaba: a window onto Plio–Pleistocene diversification processes in an arid biome

Environmental changes over the Plio‐Pleistocene have been key drivers of speciation patterns and genetic diversification in high‐latitude and mesic environments, yet comparatively little is known about the evolutionary history of species in arid environments. We applied phylogenetic and phylogeographic analyses to understand the evolutionary history of Warramaba grasshoppers from the Australian arid zone, a group including sexual and parthenogenetic lineages. Sequence data (mitochondrial COI) showed that the four major sexual lineages within Warramaba most likely diverged in the Pliocene, around 2–7 million years ago. All sexual lineages exhibited considerable phylogenetic structure. Detailed analyses of the hybrid parthenogenetic species W. virgo and its sexual progenitors showed a pattern of high phylogenetic diversity and phylogeographic structure in northern lineages, and low diversity and evidence for recent expansion in southern lineages. Northern sexual lineages persisted in localized refugia over the Pleistocene, with sustained barriers promoting divergence over this period. Southern parts of the present range became periodically unsuitable during the Pleistocene, and it is into this region that parthenogenetic lineages have expanded. Our results strongly parallel those for sexual and parthenogenetic lineages of the gecko Heteronotia from the same region, indicating a highly general effect of Plio‐Pleistocene environmental change on diversification processes in arid Australia.     

Molecular phylogenetics at the population/species interface in cave spiders of the southern Appalachians (Araneae:Nesticidae:Nesticus)

This paper focuses on the relationship between population genetic structure and speciation mechanisms in a monophyletic species group of Appalachian cave spiders (Nesticus). Using mtDNA sequence data gathered from 256 individuals, I analyzed patterns of genetic variation within and between populations for three pairs of closely related sister species. Each sister-pair comparison involves taxa with differing distributional and ecological attributes; if these ecological attributes are reflected in basic demographic differences, then speciation might proceed differently across these sister taxa comparisons. Both frequency-based and gene tree analyses reveal that the genetic structure of the Nesticus species studied is characterized by similar and essentially complete population subdivision, regardless of differences in general ecology. These findings contrast with results of prior genetic studies of cave-dwelling arthropods that have typically revealed variation in population structure corresponding to differences in general ecology. Species fragmentation through both extrinsic and intrinsic evolutionary forces has resulted in discrete, perhaps independent, populations within morphologically defined species. Large sequence divergence values observed between populations suggest that this independence may extend well into the past. These patterns of mtDNA genealogical structure and divergence imply that species as morphological lineages are currently more inclusive than basal evolutionary or phylogenetic units, a suggestion that has important implications for the study of speciation mechanisms.      

DNA evidence for morphological and cryptic Cenozoic speciations in the Anaspididae, ‘living fossils’ from the Triassic

The speciation history of Anaspides tasmaniae (Crustacea: Malacostraca) and its close relatives (family Anaspididae) was studied by phylogenetic and molecular clock analyses of mitochondrial DNA sequences. The phylogenetic analyses revealed that the Anaspides morphotype conceals at least three cryptic species belonging to different parts of its range. The occurrence of multiple cryptic phylogenetic species within one morphological type shows that substantial genetic evolution has occurred independently of morphological evolution. Molecular clock dating of the speciation events that generated both the cryptic and the morphological species of Anaspididae indicated continuous speciation within this group since the Palaeocene ~55 million years ago. This relatively constant rate of recent morphological and cryptic speciation within the Anaspididae suggests that the speciation rate in this group does not correlate with its low extinction rate or morphological conservatism.     

Testing phylogenetic hypotheses for reconstructing the evolutionary history of Dolichopoda cave crickets in the eastern Mediterranean

Aim To investigate the molecular phylogenetic divergence and historical biogeography of cave crickets belonging to the genus Dolichopoda (Orthoptera, Rhaphidophoridae). Location Caves in continental and insular Greece. Methods We sequenced 1967 bp of mitochondrial DNA, corresponding to three fragments of the small and large subunit of the ribosomal RNA (16S and 12S rRNA, respectively) and to the subunit I of cytochrome oxidase (COI), to reconstruct phylogenetic relationships among all 30 known Greek species of Dolichopoda. Alternative hypotheses about the colonization of the Hellenic Peninsula by Dolichopoda species were tested by comparing the degree of discordance between species trees and gene trees under four plausible biogeographical scenarios. Results The present study revealed a rather well resolved phylogeny at species level, identifying a number of clades that represent long‐separated lineages and diverse evolutionary histories within the genus Dolichopoda. Two main clades were revealed within Hellenic–Aegean species, identifying a north‐western and a south‐eastern species group. Based on Bayesian analysis, we applied a relaxed molecular clock to estimate the divergence times between the lineages. The results revealed that the origins of eastern Mediterranean lineages are much older than those of previously studied western Mediterranean Dolichopoda. Tests of alternative biogeographical hypotheses showed that a double colonization of the Hellenic Peninsula, following separate continental and trans‐Aegean routes during the Messinian stage, best accounts for the present distribution of Greek Dolichopoda species. Main conclusions Reconstruction and biogeographical hypothesis testing indicated that the colonization of Greece by Dolichopoda species comprised two episodes and two different routes. The southern lineage probably arose from a trans‐Aegean colonization during the Messinian salinity crisis (5.96–5.33 Ma). The northern lineage could be the result of dispersal from the north through the Balkan Peninsula. The opening of the Mid‐Aegean Trench could have promoted an initial diversification within the uprising Anatolian Plateau, while the Messinian marine regression offered the conditions for a rapid dispersal through the whole Aegean–Hellenic region. In addition, climatic events during the Plio‐Pleistocene may have been responsible for the speciation within each of the two different phylogeographical units, principally attributable to vicariance events.     

First DNA sequences from Asian cave bear fossils reveal deep divergences and complex phylogeographic patterns

Until recently, cave bears were believed to have only inhabited Europe. However, recent morphological evidence suggests that cave bears' geographic range extended as far east as Transbaikalia, Eastern Siberia. These Asian cave bears were morphologically distinct from European cave bears. However, how they related to European lineages remains unclear, stressing the need to assess the phylogenetic and phylogeographic relationship between Asian cave bears and their European relatives. In this work, we address this issue using a 227 base-pair fragment of the mitochondrial control region obtained from nine fossil bone samples from eight sites from the Urals, Caucasus, Altai Mountains, Ukraine and Yana River region in Eastern Siberia. Results of the phylogenetic analyses indicate that (i) the cave bear from the Yana River is most closely related to cave bears from the Caucasus region; (ii) the Caucasus/Yana group of bears is genetically very distinct from both European cave bears and brown bears, suggesting that these bears could represent an independent species; and (iii) the Western European cave bear lineage reached at least temporarily to the Altai Mountains, 7000 km east of their known centre of distribution. These results suggest that the diversity of cave bears was greater than previously believed, and that they could survive in a much wider range of ecological conditions than previously assumed. They also agree with recent studies on other extinct and extant species, such as wolves, hyenas and steppe bison, which have also revealed higher genetic and ecological diversity in Pleistocene populations than previously known.     

Marine biogeography of southern Australia: phylogeographical structure in a temperate sea-star

Aim To test whether marine biogeographical patterns observed at the community level are also important within species. It is postulated that historical hydrogeographic barriers have driven in situ diversification. Location The intertidal and shallow subtidal zones of southern Australia, New Zealand and nearby islands. Australia's temperate marine communities are characterized by a high degree of endemism and show strong biogeographical structure along an east–west axis. Methods Phylogeographical analysis of the widespread asteriid sea‐star Coscinasterias muricata Verrill across southern Australia and New Zealand. Forty‐two samples from 27 locations were included in phylogenetic analyses of mitochondrial (CO1; control region) and nuclear (ITS2) DNA sequences. Results Analysis of mtDNA revealed a deep phylogenetic split within Australian C. muricata, strongly correlated with latitude. ‘Northern’ haplotypes (latitude ≤ 37.6° S, nine sites, 15 samples) were 7.3–9.4% divergent from ‘southern’ haplotypes (latitude ≥ 37.6° S, 19 sites, 27 samples), consistent with late Pliocene separation. Eastern and western representatives of the ‘northern’ clade were 0.5–1.0% divergent, probably reflecting Pleistocene isolation. The ‘southern’ clade of Australia is also represented in New Zealand, indicating Pleistocene oceanic dispersal. Nuclear DNA (ITS2) sequences yielded relatively little phylogenetic resolution, but were generally congruent with mtDNA‐based groupings. Main conclusions The phylogeographical pattern detected within Australian C. muricata closely resembles marine biogeographical groupings proposed on the basis of community and species distributions. Recurring evolutionary patterns may have been driven by the hydrographic history of southern Australia. Specifically, we suggest that Plio‐Pleistocene temperature change and the repeated opening and closure of Bass Strait promoted allopatric divergence and perhaps cryptic speciation in C. muricata.     

Diversification and asymmetrical gene flow across time and space: lineage sorting and hybridization in polytypic barking frogs

Young species complexes that are widespread across ecologically disparate regions offer important insights into the process of speciation because of their relevance to how local adaptation and gene flow influence diversification. We used mitochondrial DNA and up to 28 152 genomewide single nucleotide polymorphisms from polytypic barking frogs (Craugastor augusti complex) to infer phylogenetic relationships and test for the signature of introgressive hybridization among diverging lineages. Our phylogenetic reconstructions suggest (i) a rapid Pliocene–Pleistocene radiation that produced at least nine distinct lineages and (ii) that geographic features of the arid Central Mexican Plateau contributed to two independent northward expansions. Despite clear lineage differentiation (many private alleles and high between‐lineage F_ST scores), D‐statistic tests, which differentiate introgression from ancestral polymorphism, allowed us to identify two putative instances of reticulate gene flow. Partitioned D‐statistics provided evidence that these events occurred in the same direction between clades but at different points in time. After correcting for geographic distance, we found that lineages involved in hybrid gene flow interactions had higher levels of genetic variation than independently evolving lineages. These findings suggest that the nature of hybrid compatibility can be conserved overlong periods of evolutionary time and that hybridization between diverging lineages may contribute to standing levels of genetic variation.     

Revised classification of the Cyanidiophyceae based on plastid genome data with descriptions of the Cavernulicolales ord. nov. and Galdieriales ord. nov. (Rhodophyta)

The Cyanidiophyceae, an extremophilic red algal class, is distributed worldwide in extreme environments. Species grow either in acidic hot environments or in dim light conditions (e.g., “cave Cyanidium”). The taxonomy and classification systems are currently based on morphological, eco-physiological, and molecular phylogenetic characters; however, previous phylogenetic results showed hidden diversity of the Cyanidiophyceae and suggested a revision of the classification system. To clarify phylogenetic relationships within this red algal class, we employ a phylogenomic approach based on 15 plastomes (10 new) and 15 mitogenomes (seven new). Our phylogenies show consistent relationships among four lineages (Galdieria, “cave Cyanidium”, Cyanidium, and Cyanidioschyzon lineages). Each lineage is distinguished by organellar genome characteristics. The “cave Cyanidium” lineage is a distinct clade that diverged after the Galdieria clade but within a larger monophyletic clade that included the Cyanidium and Cyanidioschyzon lineages. Because the “cave Cyanidium” lineage is a mesophilic lineage that differs substantially from the other three thermoacidophilic lineages, we describe it as a new order (Cavernulicolales). Based on this evidence, we reclassified the Cyanidiophyceae into four orders: Cyanidiales, Cyanidioschyzonales, Cavernulicolales ord. nov., and Galdieriales ord. nov. The genetic distance among these four orders is comparable to, or greater than, the distances found between other red algal orders and subclasses. Three new genera (Cavernulicola, Gronococcus, Sciadococcus), five new species (Galdieria javensis, Galdieria phlegrea, Galdieria yellowstonensis, Gronococcus sybilensis, Sciadococcus taiwanensis), and a new nomenclatural combination (Cavernulicola chilensis) are proposed.     

A SPECIATIONAL HISTORY OF “LIVING FOSSILS”: MOLECULAR EVOLUTIONARY PATTERNS IN HORSESHOE CRABS

Horseshoe crabs' exceptional morphological conservatism over the past 150 My has led to their reputation as “living fossils,” but also has served to obscure phylogenetic relationships within the complex. Here we employ nucleotide sequences from two mitochondrial genes to assess molecular evolutionary rates and patterns among all extant horseshoe crab species. The American species Limulus polyphemus proved to be the sister taxon to a clade composed of the Asiatic species Tachypleus gigas, T. tridentatus, and Carcinoscorpius rotundicauda, whose relationships inter se were not resolved definitively. Both absolute and relative rate tests suggest a moderate slowdown in sequence evolution in horseshoe crabs. Nonetheless, dates of the lineage separations remain uncertain primarily because of reservations about molecular-clock calibrations resulting from large rate variances at examined loci across Arthropods and other animal lineages, as inferred in this and prior studies. Thus, ironically, separation dates as estimated by molecular evidence in general may remain most insecure in taxonomic groups for which such information is needed most—those lacking strong biogeographic or fossil benchmarks for internal-clock calibrations. In any event, the current results show that large numbers of molecular characters distinguish even these most morphologically conservative of organisms. Furthermore, comparisons against previously published mitochondrial sequence data in the morphologically dynamic hermit crab–king crab complex demonstrates that striking heterogeneity in levels of morphotypic differentiation can characterize Arthropod lineages at similar magnitudes of molecular divergence.     

Genetic divergences pre-date Pleistocene glacial cycles in the New Zealand speckled skink, Oligosoma infrapunctatum

Aim To examine the hypothesis raised by Graham S. Hardy that Pleistocene glacial cycles suffice to explain divergence among lineages within the endemic New Zealand speckled skink, Oligosoma infrapunctatum Boulenger. Location Populations were sampled from across the entire range of the species, on the North and South Islands of New Zealand. Methods We sequenced the mitochondrial genes ND2 (550 bp), ND4 + tRNAs (773 bp) and cytochrome b (610 bp) of 45 individuals from 21 locations. Maximum likelihood, maximum parsimony and Bayesian methods were used for phylogenetic reconstruction. The Shimodaira–Hasegawa test was used to examine hypotheses about the taxonomic status of morphologically distinctive populations. Results Our analysis revealed four strongly supported clades within O. infrapunctatum. Clades were largely allopatric, except on the west coast of the South Island, where representatives from all four clades were found. Divergences among lineages within the species were extremely deep, reaching over 5%. Two contrasting phylogeographical patterns are evident within O. infrapunctatum. Main conclusions The deep genetic divisions we found suggest that O. infrapunctatum is a complex of cryptic species which diverged in the Pliocene, contrary to the existing Pleistocene‐based hypothesis. Although Pleistocene glacial cycles do not underlie major divergences within this species, they may be responsible for the shallower phylogeographical patterns that are found within O. infrapunctatum, which include a radiation of haplotypes in the Nelson and Westland regions.     

Lineage divergence and speciation in the Web‐toed Salamanders (Plethodontidae: Hydromantes) of the Sierra Nevada,California

Peripatric speciation and the importance of founder effects have long been controversial, and multilocus sequence data and coalescent methods now allow hypotheses of peripatric speciation to be tested in a rigorous manner. Using a multilocus phylogeographical data set for two species of salamanders (genus Hydromantes) from the Sierra Nevada of California, hypotheses of recent divergence by peripatric speciation and older, allopatric divergence were tested. Phylogeographical analysis revealed two divergent lineages within Hydromantes platycephalus, which were estimated to have diverged in the Pliocene. By contrast, a low‐elevation species, Hydromantes brunus, diverged from within the northern lineage of H. platycephalus much more recently (mid‐Pleistocene), during a time of major climatic change in the Sierra Nevada. Multilocus species tree estimation and coalescent estimates of divergence time, migration rate, and growth rate reject a scenario of ancient speciation of H. brunus with subsequent gene flow and introgression from H. platycephalus, instead supporting a more recent divergence with population expansion. Although the small, peripheral distribution of H. brunus suggests the possibility of peripatric speciation, the estimated founding population size of the species was too large to have allowed founder effects to be important in its divergence. These results provide evidence for both recent speciation, most likely tied to the climatic changes of the Pleistocene, and older lineage divergence, possibly due to geological events, and add to evidence that Pleistocene glacial cycles were an important driver of diversification in the Sierra Nevada.     

Deep mitochondrial introgression and hybridization among ecologically divergent vole species

The completion of speciation is typically difficult to ascertain in rapidly diverging taxa but the amount of hybridization and gene flow in sympatry or parapatry contains important information about the level of reproductive isolation achieved. Here, we examined the progress in speciation between the Mediterranean (Microtus duodecimcostatus) and the Lusitanian pine vole (M. lusitanicus), which are part of the most rapid radiation of species known in mammals. These two Iberian pine voles are classified as separate species because of differences in morphology and ecology, but relatively many ambiguous individuals can be found in sympatric conditions. Our phylogenetic analyses of rangewide data from the mitochondrial cytochrome b gene (mtDNA) demonstrated high levels of diversity and a basal separation in two parapatric lineages. However, mtDNA affiliation was at odds with morphological classification or geographical distribution of the taxa. In contrast, statistical analyses of microsatellites (nucDNA) showed two clear genetic clusters in allopatry and sympatry generally matching morphological classification. This cytonuclear discordance over a large geographic area suggests historical introgression of mtDNA from M. duodecimcostatus to M. lusitanicus. There was statistical evidence for at least two recent hybrids in the sympatry zone but gene flow is apparently low given clear‐cut differences in nucDNA. Our results indicate a relatively advanced speciation process in these Iberian pine voles without fully established reproductive isolation. This situation enables use of combined population genomic and experimental approaches for the separation of patterns and mechanisms in the ongoing explosive diversification of these and other Arvicoline rodents in the future.     

Songs,genetics, and morphology: revealing the taxonomic units in the European Cicadetta cerdaniensis cicada group,with a description of new taxa (Hemiptera: Cicadidae)

Recent acoustic studies have revealed that Cicadetta montana (Scopoli, 1772), which was once thought to be a single widespread Palaearctic cicada species, is actually a complex of many taxa. Although some song patterns are very distinct, others comprise groups of closely related species, as in the case of Cicadetta cerdaniensis Puissant & Boulard, 2000, Cicadetta cantilatrix Sueur & Puissant, 2007, and Cicadetta anapaistica Hertach, 2011. Seven spatially or behaviourally isolated metapopulations belonging to this song group from Italy and Switzerland were detected and investigated using acoustic, molecular, and morphological methods. Taxonomic decisions in this group are challenging because of a lack of truly diagnostic morphological characters, variously coloured morphs, qualitatively intermediate song patterns in contact zones, and strong temperature dependence of song‐duration characters. Molecular genetic studies suggest rapid speciation resulting in incomplete lineage sorting and introgression. It is only by using multiple sources of data that species can be delimited. The new species C icadetta sibillae sp. nov. and the new subspecies C icadetta anapaistica lucana ssp. nov. were described using the microstructure of the male calling songs. C icadetta sibillae sp. nov. occurs from southern Switzerland to central Italy, and is the most abundant cicada in the Northern Apennine. C icadetta anapaistica lucana ssp. nov. is endemic to a small southern Italian distribution range, and seems to be threatened by habitat loss and fragmentation. There is strong evidence that current distribution patterns and phylogenetic relationships of the Cicadetta cerdaniensis group are linked to speciation events in Pleistocene glacial refugia in the Italian, Iberian, and Balkan peninsulas. © 2015 The Linnean Society of London     

Revisiting the phylogeography of Asellus aquaticus in Europe: insights into cryptic diversity and spatiotemporal diversification

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Speciation with gene flow in a narrow endemic West Virginia cave salamander (Gyrinophilus subterraneus)

Due to their limited geographic distributions and specialized ecologies, cave species are often highly endemic and can be especially vulnerable to habitat degradation within and surrounding the cave systems they inhabit. We investigated the evolutionary history of the West Virginia Spring Salamander (Gyrinophilus subterraneus), estimated the population trend from historic and current survey data, and assessed the current potential for water quality threats to the cave habitat. Our genomic data (mtDNA sequence and ddRADseq-derived SNPs) reveal two, distinct evolutionary lineages within General Davis Cave corresponding to G. subterraneus and its widely distributed sister species, Gyrinophilus porphyriticus, that are also differentiable based on morphological traits. Genomic models of evolutionary history strongly support asymmetric and continuous gene flow between the two lineages, and hybrid classification analyses identify only parental and first generation cross (F1) progeny. Collectively, these results point to a rare case of sympatric speciation occurring within the cave, leading to strong support for continuing to recognize G. subterraneus as a distinct and unique species. Due to its specialized habitat requirements, the complete distribution of G. subterraneus is unresolved, but using survey data in its type locality (and currently the only known occupied site), we find that the population within General Davis Cave has possibly declined over the last 45 years. Finally, our measures of cave and surface stream water quality did not reveal evidence of water quality impairment and provide important baselines for future monitoring. In addition, our unexpected finding of a hybrid zone and partial reproductive isolation between G. subterraneus and G. porphyriticus warrants further attention to better understand the evolutionary and conservation implications of occasional hybridization between the species.

     

HOW DOES ECOLOGICAL OPPORTUNITY INFLUENCE RATES OF SPECIATION,EXTINCTION, AND MORPHOLOGICAL DIVERSIFICATION IN NEW WORLD RATSNAKES (TRIBE LAMPROPELTINI)?

Ecological adaptive radiation theory predicts an increase in both morphological and specific diversification when organisms colonize new environments. Accordingly, bursts of morphological diversification, characterized by low within‐subclade morphological disparity, may be associated with these increases in speciation rates. Conversely, increasing species density, reduction in available habitat, or increasing extinction rates are expected to cause rates of diversification to decline. We test these hypotheses by examining the tempo and mode of speciation in the lampropeltinine snakes, a morphologically variable group that colonized the New World ～24 million years ago and radiated throughout the Miocene. We show that specific diversification increased early in the history of the group, and that most morphological variation is partitioned among, rather than within subclades. These patterns provide further evidence for the hypothesis that morphological variation tends to be strongly partitioned among lineages when clades undergo early bursts of species diversification. A reduction in speciation rates may be indicative of density dependent effects due to a saturation of available ecological opportunity, rather than increases in extinction rates at the onset of the Pleistocene/Pliocene glacial cycles. This evidence runs counter to the general Pleistocene species pump model.     

A new and highly divergent mitochondrial lineage in the Small Five-toed Jerboa,Allactaga elater,from Iran (Mammalia: Rodentia)

The Small Five-toed Jerboa, Allactaga elater, is a small rodent adapted to desert and semi-arid habitats with a widespread distribution around the Caucasus. Previous studies have suggested the occurrence of subspecific variation within the species but, except for a recent phylogeny of the genus Allactaga, most of the work done on the taxonomy of the group relies on morphological data only. To contribute to the current understanding of patterns of genetic diversity of A. elater we analysed one mitochondrial locus, cytochrome b, from 13 Iranian specimens. Comparing to a recent phylogeny, our results suggest the existence of two additional mitochondrial lineages, one that clusters within previously described lineages and a new and highly divergent one. The two novel mitochondrial lineages occur in the north and form two highly divergent monophyletic groups (Dxy = 14%), which likely separated during the Pleistocene.     

Molecular phylogeny and the historical biogeography of the warblers of the genus Sylvia (Aves)

A molecular phylogeny based on DNA/DNA hybridization revealed that the Sylvia-Parisoma complex is monophyletic and includes three main groups of species, the “mid-European” warblers, the genus Parisoma, and the “eu-Mediterranean” Sylvia species sensu stricto. The latter can be assigned to three main clusters, a “West-Mediterranean” group, a “Central-Mediterranean group”, and an “East-Mediterranean” group. The radiation of the whole complex is much more ancient than formerly believed. It started ca 12–13 Ma ago and the ancestors of the main extant groups differentiated during the Pliocene. Only speciation events within the “eu-Mediterranean” lineages occurred during the Pleistocene. The paleoclimatical and paleoecological history of the Mediterranean region is too complicated to provide any evidence for direct relationships between past events and evolutionary steps of these taxa which did not leave any reliable fossil record. However, some major speciation events may be related to well documented climatical crises as well as paleobotanical data. The largely man-induced extension of matorrals over several millenia presumably extended the range of several species that were formerly much more restricted, which complicates reconstruction of the spatio-temporal course of speciation.     

Size and shape interspecific divergence patterns partly reflect phylogeny in an Onthophagus species‐complex (Coleoptera: Scarabaeidae)

Polyphenism has been suggested as an accelerator for morphological evolution and speciation. In the dung beetles of the genus Onthophagus, horn expression is polyphenic: large males develop horns whereas smaller males express greatly reduced or no horns. Horn static allometries seem to diverge rapidly amongst extant taxa, a process which might trigger changes in the male genital morphology, thus possibly promoting speciation as a by‐product. It can therefore be hypothesized that interspecific distances in allometries and, possibly, in other morphological traits mirror phylogenetic distances. In this study we first assessed the phylogenetic relationships amongst three closely related taxa belonging to the so‐called ‘Onthophagus fracticornis‐similis‐opacicollis’ species‐complex by sequencing the mitochondrial gene cytochrome oxidase subunit 1 (cox1). Biomolecular results indicated three independent lineages, the closest relationships being found between Onthophagus similis and Onthophagus opacicollis. Then we assessed the extent to which divergence pattern of horn static allometries and size and shape divergence patterns of one genital (paramere) and two nongenital (head and epipharynx) structures mirrored the phylogenetic relationships. Interspecific divergence patterns of horn static allometries, paramere, and head shape were found to be congruent with the evolutionary relationships inferred from biomolecular data. Nevertheless, paramere size and epipharynx shape showed patterns not consistent with the phylogeny. Furthermore, the relative size of nongenital structures showed little interspecific divergence compared to their shapes. Our results suggest that size and shape interspecific divergence mirror phylogeny only in part; they also indicate that distinct morphological traits may differ in their tendency to evolve in concert, and that size and shape of the same trait can evolve independently across species. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162 , 482–498.     

Historical isolation,range expansion,and secondary contact of two highly divergent mitochondrial lineages in spotted salamanders (Ambystoma maculatum)

Abstract.— The high species diversity of aquatic and terrestrial faunas in eastern North America has been attributed to range reductions and allopatric diversification resulting from historical climate change. The role these processes may have played in speciation is still a matter of considerable debate; however, their impacts on intraspecific genetic structure have been well documented. We use mitochondrial DNA sequences to reconstruct an intraspecific phylogeny of the widespread North American spotted salamander, Ambystoma maculatum , and test whether phylogenetic patterns conform to regional biogeographical hypotheses about the origins of diversity in eastern North America. Specifically, we address the number and locations of historical refugia, the extent and patterns of postglacial colonization by divergent lineages, and the origin and affinities of populations in the Interior Highland region. Despite apparent morphological uniformity, genetic discontinuities throughout the range of this species suggest that populations were historically fragmented in at least two refugia in the southern Appalachian Mountains. The ranges of these two highly divergent clades expanded northward, resulting in two widely distributed lineages that are sympatric in regions previously proposed as suture zones for other taxa. The evolutionary history of spotted salamander populations underscores the generality of biogeographical processes in eastern North America: despite differences in population size, glacial refugia, and vagility, similar signatures of differentiation are evident among and within widespread taxa.