Phylogeographic analysis of the nocturnal velvet ant genus Dilophotopsis (Hymenoptera: Mutillidae) provides insights into diversification in the Nearctic deserts

Understanding the history of diversification in the North American deserts has long been a goal of biogeographers and evolutionary biologists. Although it appears that a consensus is forming regarding the patterns of diversification in the Nearctic deserts in vertebrate taxa, little work has been done exploring the historical biogeography of widespread invertebrate taxa. Before a robust model of geobiotic change in the North American deserts can be proposed, it needs to be determined whether the same historical events affected vertebrate and invertebrate taxa in the same way. We explore the phylogeographic patterns in a widespread nocturnal wasp genus Dilophotopsis using two rDNA loci, the internal transcribed spacer regions 1 and 2 (ITS1 and ITS2). We use Bayesian phylogenetic analysis and haplotype network analysis to determine whether a consistent geographic pattern exists among species and populations within Dilophotopsis. We also used molecular dating techniques to estimate divergence dates of the major phylogenetic clades. Our analyses indicates that the species‐level divergences in Dilophotopsis occurred in the Neogene, and likely were driven by mountain building during the Miocene–Pliocene boundary (approximately 5 Mya) similar to the divergences in many vertebrate taxa. The population‐level divergences within species occurred during the Pleistocene (0.1–1.8 Mya). The present study shows that similar patterns of diversification exist in vertebrate and invertebrate taxa. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 360–375.     

Pleistocene climatic fluctuations drive isolation and secondary contact in the red diamond rattlesnake (Crotalus ruber) in Baja California

Aim

Many studies have investigated the phylogeographic history of species on the Baja California Peninsula, and they often show one or more genetic breaks that are spatially concordant among many taxa. These phylogeographic breaks are commonly attributed to vicariance as a result of geological or climatic changes, followed by secondary contact when barriers are no longer present. We use restriction‐site associated DNA sequence data and a phylogeographic model selection approach to explicitly test the secondary contact hypothesis in the red diamond rattlesnake, Crotalus ruber.

Location

Baja California and Southern California.

Methods

We used phylogenetic and population clustering approaches to identify population structure. We then used coalescent methods to simultaneously estimate population parameters and test the fit of phylogeographic models to the data. We used ecological niche models to infer suitable habitat for C. ruber at the Last Glacial Maximum (LGM).

Results

Crotalus ruber is composed of distinct northern and southern populations with a boundary near the town of Loreto in Baja California Sur. A model of isolation followed by secondary contact provides the best fit to the data, with both divergence and contact occurring in the Pleistocene. We also identify a genomic signature of northern range expansion in the northern population, consistent with LGM niche models showing that the northern‐most portion of the range of C. ruber was not suitable habitat during the LGM.

Main conclusions

We provide the first explicitly model‐based test of the secondary contact model in Baja California and show that populations of C. ruber were isolated before coming back into contact near Loreto, a region that shows phylogeographic breaks for other taxa. Given the timing of divergence and contact, we suggest that climatic fluctuations have driven the observed phylogeographic structure observed in C. ruber and that they may have driven similar patterns in other taxa.     

Phylogeography of Pseudacris regilla (Anura: Hylidae) in western North America, with a proposal for a new taxonomic rearrangement

The Baja California populations of Pseudacris regilla, a widespread species in Western North America ranging from British Columbia to southern Baja California, are characterized by extensive geographic fragmentation. We performed phylogeographic and historical demographic analyses on 609 bp of the cytochrome b mitochondrial gene of 110 individuals representing 28 populations to determine the relative influences of current and historical processes in shaping the present distribution of genetic diversity on the Baja California Peninsula. Haplotypes from this area were nested in a clade with three well-differentiated groups. Two of these groups are from Baja California Sur and another is from California and Baja California. The estimated date for the split of these groups, between 0.9-1 Ma, fits with previously proposed hypotheses of vicariance due to different transpeninsular seaways, although successive population fragmentation and expansion due to climatic oscillations during Pleistocene glaciations cannot be discarded. Historical demographic analyses detected signs of past population expansions, especially in the southernmost group. With respect to populations north of this region, two older clades were identified, one with haplotypes mainly distributed in central California, and the other corresponding to the northern half of the species range, in what apparently is a recurrent pattern in the Pacific coast of North America. Based on the concordance between mt-DNA and available allozyme data indicating that these species have a long independent evolutionary history, we propose to consider the three major clades as distinct species: P. regilla, P. pacifica, and P. hypochondriaca.     

Multilocus phylogeographic assessment of the California Mountain Kingsnake (Lampropeltis zonata) suggests alternative patterns of diversification for the California Floristic Province

Phylogeographic inference can determine the timing of population divergence, historical demographic processes, patterns of migration, and when extended to multiple species, the history of communities. Single‐locus analyses can mislead interpretations of the evolutionary history of taxa and comparative analyses. It is therefore important to revisit previous single‐locus phylogeographic studies, particularly those that have been used to propose general patterns for regional biotas and the processes responsible for generating inferred patterns. Here, we employ a multilocus statistical approach to re‐examine the phylogeography of Lampropeltis zonata. Using nonparametic and Bayesian species delimitation, we determined that there are two well‐supported species within L. zonata. Ecological niche modelling supports the delimitation of these taxa, suggesting that the two species inhabit distinct climatic environments. Gene flow between the two taxa is low and appears to occur unidirectionally. Further, our data suggest that gene flow was mediated by females, a rare pattern in snakes. In contrast to previous analyses, we determined that the divergence between the two lineages occurred in the late Pliocene (c. 2.07 Ma). Spatially and temporally, the divergence of these lineages is associated with the inundation of central California by the Monterey Bay. The effective population sizes of the two species appear to have been unaffected by Pleistocene glaciation. Our increased sampling of loci for L. zonata, combined with previously published multilocus analyses of other sympatric species, suggests that previous conclusions reached by comparative phylogeographic studies conducted within the California Floristic Province should be reassessed.     

Cryptic vicariance in Gulf of California fishes parallels vicariant patterns found in Baja California mammals and reptiles

Comparisons across multiple taxa can often clarify the histories of biogeographic regions. In particular, historic barriers to movement should have affected multiple species and, thus, result in a pattern of concordant intraspecific genetic divisions among species. A striking example of such comparative phylogeography is the recent observation that populations of many small mammals and reptiles living on the Baja California peninsula have a large genetic break between northern and southern peninsular populations. In the present study, I demonstrate that five species of near-shore fishes living on the Baja coastline of the Gulf of California share this genetic pattern. The simplest explanation for this concordant genetic division within both terrestrial and marine vertebrates is that the Baja Peninsula was fragmented by a Plio-Pleistocene marine seaway and that this seaway posed a substantial barrier to movement for near-shore fishes. For some fish species, the signal of this vicariance in mtDNA has been eroded by gene flow and is not evident with classic, equilibrium measures of population structure. Yet, significant divisions are apparent in coalescent analyses that jointly estimate divergence with gene flow. The genetic divisions within Gulf of California fishes also coincide with recognized biogeographic regions based on fish community composition and several environmental factors. It is likely that adaptation to regional environments and present-day oceanographic circulation limit gene exchange between biogeographic regions and help maintain evidence of past vicariance.     

Phylogeographic Patterns and Evolution of the Mitochondrial DNA Control Region in Two Neotropical Cats (Mammalia, Felidae)

The ocelot (Leopardus pardalis) and margay (L. wiedii) are sister-species of Neotropical cats which evolved from a lineage that migrated into South America during the formation of the Panamanian land bridge 3–5 million years ago. Patterns of population genetic divergence of each species were studied by phylogenetic analyses of mitochondrial DNA (mtDNA) control region sequences in individuals sampled across the distribution of these taxa. Abundant genetic diversity and remarkably concordant phylogeographic partitions for both species were observed, identifying parallel geographic regions which likely reflect historical faunal barriers. Inferred aspects of phylogeography, population genetic structure, and demographic history were used to formulate conservation recommendations for these species. In addition, observed patterns of sequence variation provided insight into the molecular evolution of the mtDNA control region in closely related felids. Received: 26 January 1998 / Accepted: 14 May 1998     

Phylogeography of a widespread terrestrial vertebrate in a barely-studied Palearctic region: green toads (<Emphasis Type="Italic">Bufo viridis</Emphasis> subgroup) indicate glacial refugia in Eastern Central Asia

The phylogeography of western Palearctic species is relatively well studied, but data on Eastern Central Asia are scarce. We present one of the first data sets from a widespread terrestrial vertebrate (Bufo pewzowi) inhabiting Eastern Central Asian mountains and deserts to gain knowledge on its phylogeography in this region. We applied combined phylogenetic and demographic analyses to understand the evolutionary history using mitochondrial DNA D-loop variation of toads from 37 locations. Genetic structure of Bufo pewzowi is strongly affected by landscape: we found three haplotype groups in eastern Kazakhstan, Dzungaria and Tarim Basin, divided by the Tian Shan and Dzungarian Alatau ranges. A vicariant hypothesis may explain divergence among groups. The divergence time of the three major clades was estimated about 0.9 million years ago (confidence interval 0.5–1.4), and is discussed with respect to Quaternary uplifting and glaciation in the Tian Shan. Demographic analyses provided evidence for both historical bottlenecks and population expansions and suggested Pleistocene signatures. Glacial refugia were inferred in the Tarim Basin (around the Turpan depression), in southern Dzungaria (Urumqui region), at the northern foot of the Tian Shan (Gongnaisi) and perhaps at the Altai range (Terekti). Regional Post-Last Glacial Maximum dispersal patterns are proposed. A taxonomic hypothesis is presented. This study provides a detailed history of how a widespread terrestrial vertebrate responded to geological change and Quaternary glacial events in Eastern Central Asia and may have significance for future phylogeographic research in this understudied region.     

Phylogeography and systematics of the Peromyscus eremicus species group and the historical biogeography of North American warm regional deserts

Phylogeographic relationships among 26 populations from throughout the geographic range of the Peromyscus eremicus species group are described based on sequence data for a 699-bp fragment of the mitochondrial DNA COIII gene. Distance, maximum-likelihood, and maximum-parsimony analyses of phylogenetic trees generated under four separate character-weighting strategies and representing five alternative biogeographic hypotheses revealed the existence of a cryptic species (Peromyscus fraterculus, previously included under P. eremicus) on the Baja California Peninsula and adjacent southwestern California and two distinct forms of P. eremicus, one from the Mojave, Sonoran, and northwestern Chihuahuan regional deserts (West) and one from the remainder of the Chihuahuan Desert (East). Distinctiveness of P. fraterculus is supported by previous morphometric and allozyme analyses, including comparisons with neighboring P. eremicus and parapatric P. eva, with which P. fraterculus shares a sister taxon relationship. Divergence of the eva + fraterculus, West + East eremicus, and P. merriami haplotype lineages likely occurred in the late Neogene (3 Ma), in response to northern extension of the Sea of Cortéz and elevation of the Sierra Madre Occidental; divergence of eva from fraterculus is concordant with the existence of a trans-Peninsular seaway during the Pleistocene (1 Ma); and divergence of West from East eremicus occurred during the Pleistocene pluvial-interpluvial cycles, but well before the Wisconsinan glacial interval. The sequence of divergence within the eremicus species group and causal association of geological events of the Neogene and Holocene provide a working hypothesis against which phylogeographic patterns among other arid-adapted species of the warm regional deserts of North America may be compared.     

鸟类分子系统地理学研究进展

分子系统地理学是当代生物地理学的重要分支,是以分子生物学方法重建种内和种上水平的系统发育关系,阐释进化历史,并通过分析近缘生物类群的系统发育关系与其空间和时间分布格局间的相关性构建生物区系历史的研究,是分子生物学与生物地理学结合的产物。中性进化学说和溯祖理论分析的建立,以及线粒体DNA和微卫星标记等分子遗传标记的应用,为分子系统地理学研究的开展提供了理论和实践基础。近年来,分子系统地理方法在鸟类学研究中的应用揭示了许多不同于传统认知的发现,为准确而深入的了解鸟类分子系统地理格局的差异和不同类群的起源中心提供了新颖的证据。目前的研究多从隔离分化说和扩散说的角度对鸟类分子系统地理格局的成因进行分析,而迁徙行为不同对鸟类系统地理格局的影响为成因的解释提供了新的角度。结合区域特点的比较分子系统地理研究,在更广泛的地域和更多类群中开展研究是我国鸟类分子系统地理研究的方向。此外,展望了第二代测序技术对分子生态生物地理研究具有的潜在促进作用。     

Drift effects on the multivariate floral phenotype of Calceolaria polyrhiza during a post‐glacial expansion in Patagonia

Quaternary environmental changes substantially impacted the landscape and promoted rapid evolutionary changes in many species; however, analyses of adaptive phenotypic variation in plants have usually neglected the underlying historical context. Here, we associate phylogeography and phenotypic evolution by analysing the divergence of Calceolaria polyrhiza multivariate floral phenotype after a Pleistocene post‐glacial expansion in Patagonia. Phenotypic matrix ( P ) properties (size, shape, orientation and phenotypic integration) of six refugium and six recent populations from two different phylogroups were compared following different approaches. We found that P ‐matrix shape and orientation remained stable despite the strong phylogeographic footprint of post‐glacial expansion. However, average proportional reductions in matrix size supported the expectation that drift had a significant effect on the floral phenotype in the northern phylogroup. When phylogeographic history was not included in the analyses, the results overestimated phenotypic differences, whereas under explicit phylogeographic control, drift appeared as the best explanation for matrix differences. In general, recent populations showed a larger phenotypic divergence among them, but a lower overall phenotypic variation than refugium populations. Random Skewers analyses indicated a lower potential response to selection in recently colonized populations than in refugium populations. We discuss that the combination of phylogeographic analyses with geographical distribution of functional phenotypic (genotypic) variation is critical not only to understand how historical effects influence adaptive evolution, but also to improve field comparisons in evolutionary ecology studies.     

Phylogeographic diversification of antelope squirrels (Ammospermophilus) across North American deserts

We investigated the biogeographic history of antelope squirrels, genus Ammospermophilus, which are widely distributed across the deserts and other arid lands of western North America. We combined range‐wide sampling of all currently recognized species of Ammospermophilus with a multilocus data set to infer phylogenetic relationships. We then estimated divergence times within identified clades of Ammospermophilus using fossil‐calibrated and rate‐calibrated molecular clocks. Lastly, we explored generalized distributional changes of Ammospermophilus since the last glacial maximum using species distribution models, and assessed responses to Quaternary climate change by generating demographic parameter estimates for the three wide‐ranging clades of A. leucurus. From our phylogenetic estimates we inferred strong phylogeographic structure within Ammospermophilus and the presence of three well‐supported major clades. Initial patterns of historical divergence were coincident with dynamic alterations in the landscape of western North America, and the formation of regional deserts during the Late Miocene and Pliocene. Species distribution models and demographic parameter estimates revealed patterns of recent population expansion in response to glacial retreat. When combined with evidence from co‐distributed taxa, the historical biogeography of Ammospermophilus provides additional insight into the mechanisms that impacted diversification of arid‐adapted taxa across the arid lands of western North America. We propose species recognition of populations of the southern Baja California peninsula to best represent our current understanding of evolutionary relationships among genetic units of Ammospermophilus. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 949–967.     

Phylogeography of the tidewater goby, Eucyclogobius newberryi (Teleostei, Gobiidae), in coastal California

The tidewater goby, Eucyclogobius newberryi, inhabits discrete, seasonally closed estuaries and lagoons along approximately 1500 km of California coastline. This species is euryhaline but has no explicit marine stage, yet population extirpation and recolonization data suggest tidewater gobies disperse intermittently via the sea. Analyses of mitochondrial control region and cytochrome b sequences demonstrate a deep evolutionary bifurcation in the vicinity of Los Angeles that separates southern California populations from all more northerly populations. Shallower phylogeographic breaks, in the vicinities of Seacliff, Point Buchon, Big Sur, and Point Arena segregate the northerly populations into five groups in three geographic clusters: the Point Conception and Ventura groups between Los Angeles and Point Buchon, a lone Estero Bay group from central California, and San Francisco and Cape Mendocino groups from northern California. The phylogenetic relationships between and patterns of molecular diversity within the six groups are consistent with repeated, and sometimes rapid, northward and southward range expansions out of central California caused by Quaternary climate change. Plio-Pleistocene tectonism, Quaternary coastal geography and hydrography, and historical human activities probably also influenced the modern geographic and genetic structure of E. newberryi. The phylogeography of E. newberryi is concordant with phylogeographic patterns in several other coastal California taxa, suggesting common extrinsic factors have had similar effects on different species. However, there is no evidence of a phylogeographic break coincident with a biogeographic boundary at Point Conception.     

Contrasting phylogeographic patterns in Sphagnum fimbriatum and Sphagnum squarrosum (Bryophyta, Sphagnopsida) in Europe

The chloroplast phylogeography of two peat mosses (Sphagnum fimbriatum and Sphagnum squarrosum) with similar distributions but different life history characteristics was investigated in Europe. Our main aim was to test whether similar distributions reflect similar phylogeographic and phylodemographic processes. Accessions covering the European distributions of the species were collected and approx. 2000 bp of the chloroplast genome of each species was sequenced. Maximum parsimony, statistical parsimony and phylodemographic analyses were used to address the question of whether these species with similar distributions show evidence of similar phylogeographic and phylodemographic processes. The chloroplast haplotypes of the currently spreading species S. fimbriatum showed strong geographic structure, whereas those of S. squarrosum, which has stable historical population sizes, showed only very weak geographic affinity and were widely distributed. We hypothesize that S. fimbriatum survived the last glaciations along the Atlantic coast of Europe, whereas S. squarrosum had numerous, scattered refugia in Europe. The dominance of one haplotype of S. fimbriatum across almost all of Europe suggests rapid colonization after the last glacial maximum. We hypothesize that high colonizing ability is an inherent characteristic of the species and its recent expansion in Europe is a response to climate change.     

Limited Phylogeographic Signal in Sex-Linked and Autosomal Loci Despite Geographically,Ecologically, and Phenotypically Concordant Structure of mtDNA Variation in the Holarctic Avian Genus Eremophila

Phylogeographic studies of Holarctic birds are challenging because they involve vast geographic scale, complex glacial history, extensive phenotypic variation, and heterogeneous taxonomic treatment across countries, all of which require large sample sizes. Knowledge about the quality of phylogeographic information provided by different loci is crucial for study design. We use sequences of one mtDNA gene, one sex-linked intron, and one autosomal intron to elucidate large scale phylogeographic patterns in the Holarctic lark genus Eremophila. The mtDNA ND2 gene identified six geographically, ecologically, and phenotypically concordant clades in the Palearctic that diverged in the Early - Middle Pleistocene and suggested paraphyly of the horned lark (E. alpestris) with respect to the Temminck''s lark (E. bilopha). In the Nearctic, ND2 identified five subclades which diverged in the Late Pleistocene. They overlapped geographically and were not concordant phenotypically or ecologically. Nuclear alleles provided little information on geographic structuring of genetic variation in horned larks beyond supporting the monophyly of Eremophila and paraphyly of the horned lark. Multilocus species trees based on two nuclear or all three loci provided poor support for haplogroups identified by mtDNA. The node ages calculated using mtDNA were consistent with the available paleontological data, whereas individual nuclear loci and multilocus species trees appeared to underestimate node ages. We argue that mtDNA is capable of discovering independent evolutionary units within avian taxa and can provide a reasonable phylogeographic hypothesis when geographic scale, geologic history, and phenotypic variation in the study system are too complex for proposing reasonable a priori hypotheses required for multilocus methods. Finally, we suggest splitting the currently recognized horned lark into five Palearctic and one Nearctic species.     

Comparative Phylogeography in Rainforest Trees from Lower Guinea,Africa

Comparative phylogeography is an effective approach to assess the evolutionary history of biological communities. We used comparative phylogeography in fourteen tree taxa from Lower Guinea (Atlantic Equatorial Africa) to test for congruence with two simple evolutionary scenarios based on physio-climatic features 1) the W-E environmental gradient and 2) the N-S seasonal inversion, which determine climatic and seasonality differences in the region. We sequenced the trnC-ycf6 plastid DNA region using a dual sampling strategy: fourteen taxa with small sample sizes (dataset 1, mean n = 16/taxon), to assess whether a strong general pattern of allele endemism and genetic differentiation emerged; and four taxonomically well-studied species with larger sample sizes (dataset 2, mean n = 109/species) to detect the presence of particular shared phylogeographic patterns. When grouping the samples into two alternative sets of two populations, W and E, vs. N and S, neither dataset exhibited a strong pattern of allelic endemism, suggesting that none of the considered regions consistently harboured older populations. Differentiation in dataset 1 was similarly strong between W and E as between N and S, with 3–5 significant F _ST tests out of 14 tests in each scenario. Coalescent simulations indicated that, given the power of the data, this result probably reflects idiosyncratic histories of the taxa, or a weak common differentiation pattern (possibly with population substructure) undetectable across taxa in dataset 1. Dataset 2 identified a common genetic break separating the northern and southern populations of Greenwayodendron suaveolens subsp. suaveolens var. suaveolens, Milicia excelsa, Symphonia globulifera and Trichoscypha acuminata in Lower Guinea, in agreement with differentiation across the N–S seasonal inversion. Our work suggests that currently recognized tree taxa or suspected species complexes can contain strongly differentiated genetic lineages, which could lead to misinterpretation of phylogeographic patterns. Therefore the evolutionary processes of such taxa require further study in African tropical rainforests.     

Comparative phylogeography as an integrative approach to historical biogeography

Phylogeography has become a powerful approach for elucidating contemporary geographical patterns of evolutionary subdivision within species and species complexes. A recent extension of this approach is the comparison of phylogeographic patterns of multiple co-distributed taxonomic groups, or 'comparative phylogeography.' Recent comparative phylogeographic studies have revealed pervasive and previously unrecognized biogeographic patterns which suggest that vicariance has played a more important role in the historical development of modern biotic assemblages than current taxonomy would indicate. Despite the utility of comparative phylogeography for uncovering such 'cryptic vicariance', this approach has yet to be embraced by some researchers as a valuable complement to other approaches to historical biogeography. We address here some of the common misconceptions surrounding comparative phylogeography, provide an example of this approach based on the boreal mammal fauna of North America, and argue that together with other approaches, comparative phylogeography can contribute importantly to our understanding of the relationship between earth history and biotic diversification.     

Phylogeography of a stream-dwelling frog (Pseudacris cadaverina) in southern California

Recent phylogeographic studies of animal taxa in California have revealed common geographic patterns of evolutionary divergence and genetic diversity that are generally attributable to landscape influences. However, there remains a paucity of knowledge on the evolution of freshwater taxa in southern California. Here, we investigate phylogeographic patterns in a stream-dwelling frog (Pseudacris cadaverina). Two hundred and twenty-one individuals were collected from 46 populations across the species’ range in southern California. Using 1100 bp of sequence data from cytochrome b and tRNA-Glu, we conducted phylogenetic analyses, analysis of molecular variance, and nested clade phylogeographic analysis to gain insight into the factors contributing to the distribution of genetic diversity in P. cadaverina. We tested for evidence of two putative phylogeographic breaks and tested hypotheses that genetic diversity in this species is partitioned into (1) major watersheds, (2) mountain ranges, and (3) coastal and desert regions. Our results suggest that the eastern Transverse Ranges are the center of origin for extant P. cadaverina lineages and that the observed genetic structure in this species was established during the Pleistocene Epoch. There is strong support for three major haplotype groups and a Transverse Range break in P. cadaverina that is concordant with breaks found in numerous other taxa. The distribution of genetic diversity in P. cadaverina is due in large part to the separation of populations into different major watersheds and mountain ranges. Gene flow appears to be generally limited among disjunct populations throughout the region and some desert populations have been isolated by historical habitat fragmentation.     

Comparative Phylogeography of Mesoamerican Highland Rodents: Concerted versus Independent Response to Past Climatic Fluctuations

The phylogeography of Sumichrast's harvest mouse (Reithrodontomys sumichrasti) was examined through maximum-likelihood and parsimony analyses of 1,130 bp of mitochondrial Cytochrome b sequence data from 43 individuals. The phylogeography of this Middle American highland forest-dwelling species was compared to that previously published for the codistributed Aztec deer mouse complex (Peromyscus aztecus/Peromyscus hylocetes complex) in order to test competing hypotheses of concerted versus independent responses of codistributed forms to past climatic fluctuations. Qualitatively, there were strong similarities in the phylogeographic patterns of the two groups, yet there were also areas of incongruence. Likelihood-ratio tests (Kishino-Hasegawa-Templeton and parametric bootstrap tests) indicated that this incongruence is significant and cannot be attributed simply to uncertainty in phylogenetic estimation, thereby falsifying the concerted-response hypothesis. Conversely, tree-reconciliation analysis of the area relationships inferred for each group separately indicated that there has been a significant history of covicariance between the two groups, falsifying the independent-response hypothesis. It appears that codistributed taxa in the geologically complex highlands of Mesoamerica share more common biogeographical history than can be accounted for by the independent-response hypothesis yet have not responded to past climatic fluctuations in the lock-step fashion predicted by the concerted-response hypothesis.     

A multilocus perspective on the speciation history of a North American aridland toad (Anaxyrus punctatus)

Interpretations of phylogeographic patterns can change when analyses shift from single gene-tree to multilocus coalescent analyses. Using multilocus coalescent approaches, a species tree and divergence times can be estimated from a set of gene trees while accounting for gene-tree stochasticity. We utilized the conceptual strengths of a multilocus coalescent approach coupled with complete range-wide sampling to examine the speciation history of a broadly distributed, North American warm-desert toad, Anaxyrus punctatus. Phylogenetic analyses provided strong support for three major lineages within A. punctatus. Each lineage broadly corresponded to one of three desert regions. Early speciation in A. punctatus appeared linked to late Miocene-Pliocene development of the Baja California peninsula. This event was likely followed by a Pleistocene divergence associated with the separation of the Chihuahuan and Sonoran Deserts. Our multilocus coalescent-based reconstruction provides an informative contrast to previous single gene-tree estimates of the evolutionary history of A. punctatus.     

Phylogeographic patterns in widespread corvid birds

Intraspecific genetic diversity and phylogeography of Corvus corone was investigated using the mitochondrial (mt) control region as a molecular marker. A split into two distinct mt lineages was observed. One represents individuals from a wide geographic range spanning from England to the Russian Far East (Kamchatka), while the other one was found in the Primorye and Khabarovsk regions (southern parts of Russian Far East) as well as Japan. For comparison, we investigated several widespread Palearctic corvid taxa with respect to their phylogeographic patterns. A deep split into two lineages was revealed in five cases: Besides C. corone, within Corvus frugilegus, Pica pica, and between the species pairs Corvus monedula-Corvus dauuricus and Cyanopica cyanus-Cyanopica cooki. Although these taxa display a variety of distribution patterns, from disjunct, para/allopatric to continuous, the genetic pattern and level of divergence between clades is very similar. This implies that the differentiation started in about the same time range. In contrast, no differentiation into highly divergent lineages was detected in Corvus corax, Perisoreus infaustus, and Nucifraga caryocatactes. We try to explain the two phylogeographic patterns in corvid birds with ecological factors accompanying the changing climatic conditions during the Pleistocene. The deep genetic splits within several widely distributed Palearctic corvids are discussed with respect to taxonomic questions.