Speciational history of Australian grass finches (Poephila) inferred from thirty gene trees

Multilocus genealogical approaches are still uncommon in phylogeography and historical demography, fields which have been dominated by microsatellite markers and mitochondrial DNA, particularly for vertebrates. Using 30 newly developed anonymous nuclear loci, we estimated population divergence times and ancestral population sizes of three closely related species of Australian grass finches (Poephila) distributed across two barriers in northern Australia. We verified that substitution rates were generally constant both among lineages and among loci, and that intralocus recombination was uncommon in our dataset, thereby satisfying two assumptions of our multilocus analysis. The reconstructed gene trees exhibited all three possible tree topologies and displayed considerable variation in coalescent times, yet this information provided the raw data for maximum likelihood and Bayesian estimation of population divergence times and ancestral population sizes. Estimates of these parameters were in close agreement with each other regardless of statistical approach and our Bayesian estimates were robust to prior assumptions. Our results suggest that black-throated finches (Poephila cincta) diverged from long-tailed finches (P. acuticauda and P. hecki) across the Carpentarian Barrier in northeastern Australia around 0.6 million years ago (mya), and that P. acuticauda diverged from P. hecki across the Kimberley Plateau-Arnhem Land Barrier in northwestern Australia approximately 0.3 mya. Bayesian 95% credibility intervals around these estimates strongly support Pleistocene timing for both speciation events, despite the fact that many gene divergences across the Carpentarian region clearly predated the Pleistocene. Estimates of ancestral effective population sizes for the basal ancestor and long-tailed finch ancestor were large (about 521,000 and about 384,000, respectively). Although the errors around the population size parameter estimates are considerable, they are the first for birds taking into account multiple sources of variance.     

Allometric relations in three species of finches (Aves: Fringillidae)

Static nestling, adult and ontogenetic allometry were analysed in three species of finches. Static nestling allometry was very similar across age in early ontogeny and among species and could be approximated by a single matrix of phenotypic variances and covariances. The first eigenvector of this matrix showed negative allometry of bill and tarsus to mass, but positive for wing length to mass. Adult static allometry was also very similar among species, but differed from nestling pattern. In adults the bill had a positive allometry in relation to tarsus and wing, but negative to mass, while tarsus and wing were unrelated to mass. The ontogenetic allometry in each species was very similar to nestling static allometry. Viewed in relation to final size, bill characters grew more slowly than body characters, but for a longer time, which created the difference between adult and nestling allometric patterns. There were differences among species both with regard to elevation and slope of allometric coefficients, suggesting that the differences among species came about by changes in the three fundamental ontogenetic parameters namely growth rate, onset of growth and offset of growth.     

Patterns of morphological variation among cardueline finches (Fringillidae: Carduelinae)

Patterns of variation in five morphological traits in cardueline finches were analysed. Among species, bill characters were the most and tail length the least variable. Species differed primarily in terms of body size, whereas genera differed in terms of bill size. Cardueline finches were far less variable compared with the amount of variation expected under a model of neutral random drift. This indicates that this group of birds is under strong stabilizing selection pressure. This could conform to models of stasis where populations are thought to travel only between adjacent adaptive peaks separated by shallow valleys. Changes in body size are correlated with speciation, whereas changes in bill morphology are correlated with divergences leading to the erection of new genera.     

Suprageneric systematics of flea beetles (Chrysomelidae: Alticinae) inferred from multilocus sequence data

Recent phylogenetic studies of flea beetles (Alticinae) based on morphological or molecular data have focused on the relationship and possible paraphyly with respect to the closely related Galerucinae, while the supra-generic classification mainly dates back to the 19th century. Here, phylogenetic analysis was performed on DNA sequences for two mitochondrial (rrnL and cox1) and two nuclear (SSU and LSU rRNA) genes from 158 genera and 165 species that cover most suprageneric groups of flea beetles proposed in the older literature. Various alignment strategies and tree search methods were used to test the stability of major clades. Besides confirmation of the placement of several alticine lineages within Galerucinae, a preliminary framework for classification of the main alticine clades was obtained. It is proposed to recognize 18 groups of genera based on well-supported nodes. These include the Altica, Amphimela, Aphthona, Blepharida, Chabria, Chaetocnema, Dibolia, Disonycha, Griva, Lactica, Longitarsus, Manobia, Monoplatus, Nisotra, Oedionychis, Pentamesa, Phygasia and Pseudodera groups. These groups provide a novel perspective to the existing classification. The analysis of 14 morphological characters used in the traditional classification of Alticinae and Galerucinae revealed high levels of homoplasy with respect to the DNA-based tree, but significant hierarchical structure in most of them. Even if not unique to any particular group of genera, these traits largely corroborate the groupings established with DNA sequences.     

Ancestrality and evolution of trait syndromes in finches (Fringillidae)

Species traits have been hypothesized by one of us (Ponge, 2013) to evolve in a correlated manner as species colonize stable, undisturbed habitats, shifting from “ancestral” to “derived” strategies. We predicted that generalism, r‐selection, sexual monomorphism, and migration/gregariousness are the ancestral states (collectively called strategy A) and evolved correlatively toward specialism, K‐selection, sexual dimorphism, and residence/territoriality as habitat stabilized (collectively called B strategy). We analyzed the correlated evolution of four syndromes, summarizing the covariation between 53 traits, respectively, involved in ecological specialization, r‐K gradient, sexual selection, and dispersal/social behaviors in 81 species representative of Fringillidae, a bird family with available natural history information and that shows variability for all these traits. The ancestrality of strategy A was supported for three of the four syndromes, the ancestrality of generalism having a weaker support, except for the core group Carduelinae (69 species). It appeared that two different B‐strategies evolved from the ancestral state A, both associated with highly predictable environments: one in poorly seasonal environments, called B1, with species living permanently in lowland tropics, with “slow pace of life” and weak sexual dimorphism, and one in highly seasonal environments, called B2, with species breeding out‐of‐the‐tropics, migratory, with a “fast pace of life” and high sexual dimorphism.     

The phylogenetic relationships and generic limits of finches (Fringillidae)

Phylogenetic relationships among the true finches (Fringillidae) have been confounded by the recurrence of similar plumage patterns and use of similar feeding niches. Using a dense taxon sampling and a combination of nuclear and mitochondrial sequences we reconstructed a well resolved and strongly supported phylogenetic hypothesis for this family. We identified three well supported, subfamily level clades: the Holoarctic genus Fringilla (subfamly Fringillinae), the Neotropical Euphonia and Chlorophonia (subfamily Euphoniinae), and the more widespread subfamily Carduelinae for the remaining taxa. Although usually separated in a different family-group taxon (Drepanidinae), the Hawaiian honeycreepers are deeply nested within the Carduelinae and sister to a group of Asian Carpodacus. Other new relationships recovered by this analysis include the placement of the extinct Chaunoproctus ferreorostris as sister to some Asian Carpodacus, a clade combining greenfinches (Carduelis chloris and allies), Rhodospiza and Rhynchostruthus, and a well-supported clade with the aberrant Callacanthis and Pyrrhoplectes together with Carpodacus rubescens. Although part of the large Carduelis-Serinus complex, the poorly known Serinus estherae forms a distinct lineage without close relatives. The traditionally delimited genera Carduelis, Serinus, Carpodacus, Pinicola and Euphonia are polyphyletic or paraphyletic. Based on our results we propose a revised generic classification of finches and describe a new monotypic genus for Carpodacus rubescens.     

Diversity despite dispersal: colonization history and phylogeography of Hawaiian crab spiders inferred from multilocus genetic data

The Hawaiian archipelago is often cited as the premier setting to study biological diversification, yet the evolution and phylogeography of much of its biota remain poorly understood. We investigated crab spiders (Thomisidae, Mecaphesa ) that demonstrate contradictory tendencies: (i) dramatic ecological diversity within the Hawaiian Islands, and (ii) accompanying widespread distribution of many species across the archipelago. We used mitochondrial and nuclear genetic data sampled across six islands to generate phylogenetic hypotheses for Mecaphesa species and populations, and included penalized likelihood molecular clock analyses to estimate arrival times on the different islands. We found that 17 of 18 Hawaiian Mecaphesa species were monophyletic and most closely related to thomisids from the Marquesas and Society Islands. Our results indicate that the Hawaiian species evolved from either one or two colonization events to the archipelago. Estimated divergence dates suggested that thomisids may have colonized the Hawaiian Islands as early as ~10 million years ago, but biogeographic analyses implied that the initial diversification of this group was restricted to the younger island of Oahu, followed by back-colonizations to older islands. Within the Hawaiian radiation, our data revealed several well-supported genetically distinct terminal clades corresponding to species previously delimited by morphological taxonomy. Many of these species are codistributed across multiple Hawaiian Islands and some exhibit genetic structure consistent with stepwise colonization of islands following their formation. These results indicate that dispersal has been sufficiently limited to allow extensive ecological diversification, yet frequent enough that interisland migration is more common than speciation.     

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.     

A molecular phylogeny of bullfinches Pyrrhula Brisson, 1760 (Aves: Fringillidae)

We present a molecular phylogeny of bullfinches (Pyrrhula Brisson, 1760) based on 2357bp DNA sequence information of mitochondrial genes (cyt-b, 16S rRNA) and nuclear introns (fib-7, GAPDH-11). The genus is clearly a monophyletic group. Within the limits of Pyrrhula, molecular methods support the subdivision of three main groups: (1) "Southeast-Asian bullfinches" (P. nipalensis and P. leucogenis), (2) "Himalayan bullfinches" (P. aurantiaca, P. erythaca, P. erythrocephala), and (3) "Eurasian bullfinches" (P. pyrrhula s.l.). Within the last group there are four different subgroups: (3a) P. (p.) murina, (3b) P. (p.) cineracea, (3c) P. (p.) griseiventris, and (3d) P. pyrrhula s.str. The centre of origin of the genus Pyrrhula was most probably Southeast Asia. Incomplete lineage sorting of both mitochondrial and nuclear genes is observed among two apparently good species (P. erythaca and P. erythrocephala) indicating a very recent speciation event within the Himalayan Mountain chain. According to our estimates, the Pyrrhula ancestors split from the Pinicola ancestors before the Pleistocene. Apart from the subsequent Pre-Pleistocene splits of the three ancestral main groups, most of the diversification of today's representatives probably took place during the past 600,000 years, possibly in interaction with Pleistocene refugia and successive colonization movements after the last glaciation. Thus our work confirms the traditional delimitation of the bullfinches towards the other members of the finch family Fringillidae and corroborates most of the classic intra-generic subdivisions.     

A multilocus phylogeny of the Sulidae (Aves: Pelecaniformes)

Gene trees will often differ from the true species history, the species tree, as a result of processes such as incomplete lineage sorting. New methods such as Bayesian Estimation of the Species Tree (BEST) use the multispecies coalescent to model lineage sorting, and directly infer the species tree from multilocus DNA sequence data. The Sulidae (Aves: Pelecaniformes) is a family of ten booby and gannet species with a global distribution. We sequenced five nuclear intron loci and one mitochondrial locus to estimate a species tree for the Sulidae using both BEST and by concatenating nuclear loci. We also used fossil calibrated strict and relaxed molecular clocks in BEAST to estimate divergence times for major nodes in the sulid phylogeny. Individual gene trees showed little phylogenetic conflict but varied in resolution. With the exception of the mitochondrial gene tree, no gene tree was completely resolved. On the other hand, both the BEST and concatenated species trees were highly resolved, strongly supported, and topologically consistent with each other. The three sulid genera (Morus, Sula, Papasula) were monophyletic and the relationships within genera were mostly consistent with both a previously estimated mtDNA gene tree and the mtDNA gene tree estimated here. However, our species trees conflicted with the mtDNA gene trees in the relationships among the three genera. Most notably, we find that the endemic and endangered Abbott's booby (Papasula abbotti) is likely basal to all other members of the Sulidae and diverged from them approximately 22 million years ago.     

Recent colonization and radiation of North American Lycaeides (Plebejus) inferred from mtDNA

North American Lycaeides populations exhibit remarkable variation in ecological, morphological, and behavioral characters, as well as an established history of introgressive hybridization. We examined mitochondrial DNA variation from 55 Eurasian and North American Lycaeides populations using molecular phylogenetics and coalescent-based methods in order to clarify the evolutionary and demographic history of this polytypic group. Specifically we addressed the following questions: (1) Do mitochondrial alleles sampled from North America form a monophyletic group, which would be expected if North American Lycaeides were descended from a single Eurasian ancestor? (2) When did Lycaeides colonize North America? and (3) What is the demographic history of North American Lycaeides since their colonization? Bayesian maximum likelihood methods identified three major mitochondrial lineages for Lycaeides; each lineage contained haplotypes sampled from both Eurasia and North America. This suggests a complex colonization history for Lycaeides, which likely involved multiple founding lineages. Coalescent-based analyses placed the colonization of North America by Eurasian Lycaeides sometime during or after the late Pliocene. This was followed by a sudden increase in population size of more than an order of magnitude for the North American population of Lycaeides approximately 100,000-150,000 years before the present. These mitochondrial data, in conjunction with data from previous ecological, morphological, and behavioral studies, suggest that the diversity observed in Lycaeides in North America is the result of a recent evolutionary radiation, which may have been facilitated, in part, by hybridization.     

Characters discriminating two seed husking mechanisms in finches (Fringillidae: Carduelinae) and estrildids (Passeridae: Estrildinae)

Finches have two major types of seed husking, each with two phases: crushing and seed husk disposal. Recent observations show that both Spice Finches and Greenfinches husk seeds by a crushing mechanism, but the Greenfinch, Carduelis chloris, applies mediolateral movements of the lower mandible, especially during seek husk disposal, while such movements are not-found in the Spice Finch, Lonchura punctulata. A detailed comparison of the anatomies of their jaw apparatuses elucidates that numerous discriminating characters form an integrated complex that parallels the difference in seed husking. These focus on 1) a more flattened shape of the articular facets in the quadratomandibular articulation and a lack of the postorbital ligament, resulting in decoupling of the quadratomandibular joint facets, and release of the pseudotemporal muscle from jaw elevation only and 2) adductor mandibulae and pterygoid muscles with an increased medial component in the Greenfinch. Muscles built heavier in the Greenfinch than the Spice Finch, especially mediolaterally oriented muscles, are in concurrence with muscle asymmetries found in crossbills (Loxia sp.), a finch-species employing unilateral mandibular rotation. These two groups of differences are conditions to transform a dorsoventrally oriented into an improved, mediolaterally oriented husking design. These features, though in concert with many others, are proposed as they key innovations that released the increase of crushing forces by extending forces from jaw muscles and improvement of the disposal of the crushed shell by left-right lower mandible manipulation. Such an improved husking capacity may have opened the vast food-array of hard-shelled, dicotyledon seeds, allowing extensive trophic radiation. J. Morphol 232:1–33, 1997. © 1997 Wiley-Liss, Inc.     

Quantitative trait and allozyme divergence in the Greenfinch (Carduelis chloris, Aves: Fringillidae)

Quantitative trait divergence and variability among 12 greenfinch populations across continental Europe was examined and compared to divergence in neutral genetic markers (allozymes). The added among locality variance component for 16 skeletal traits was large (mean 28%, range 4–48%) equalling a divergence of up to three SD units. The divergence in quantitative traits (Qst = 0.04-0.48) greatly exceeded that in alloymes (F_ST= 0.01-0.07), indicating the differentiation in quantitative traits to be larger than expected by mutation and drift alone. This conclusion was consistent also with results from the multivariate approach of Rogers & Harpending. However, genetic and morphometric distances between populations were positively correlated, even when controlling for the geographic distance separating pairs of populations. In concordance with Bergmann's rule, most traits were strongly and positively correlated with latitude, indicating latitudinally ordered genetic or/and environmental effects. However, the correlation between lower mandible width and latitude was strongly negative, demonstrating an inverse relationship between beak size and body size across the populations. These results are interpreted to reflect the re-colonization of history of northern Europe (genetic and geographic distances correlated) which has been paralleled by selection acting on quantitative traits (Q_ST>F_ST)- In particular, the counter-gradient variation in beak width, a functionally important trait, is suggestive of an adaptive basis for quantitative trait divergence.     

Patterns of speciation inferred from mitochondrial DNA in North American Chthamalus (Cirripedia: Balanomorpha: Chthamaloidea)

Chthamalus is a cosmopolitan genus of high intertidal barnacles that are difficult to distinguish morphologically. This study focuses on a single subgeneric group of Chthamalus that is found on the coasts of North and Central America to determine the age and pattern of speciation among these species. Two comparisons of genetic divergence are made across the Panamanian Isthmus, allowing estimates of the substitution rate to be made for two mitochondrial genes coding for COI and 16S rRNA in these barnacles. These data suggest that the little morphological diversification that there has been in Chthamalus occurred early in the history of the genus, and subsequent radiations were probably induced by transient periods of population separation during late Miocene to Recent climatic changes.     

Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondrial markers

Gulls (Aves: Laridae) constitute a recent and cosmopolite family of well-studied seabirds for which a robust phylogeny is needed to perform comparative and biogeographical analyses. The present study, the first molecular phylogeny of all Larids species (N=53), is based on a combined segment of mtDNA (partial cytochrome b and control region). We discuss our phylogenetic tree in the light of previous suggestions based on morphological, behavioral, and plumage characters. Although the phylogeny is not fully resolved, it highlights several robust species groups and confirms or identifies for the first time some sister relationships that had never been suggested before. The Dolphin Gull (Leucophaeus scoresbii) for instance, is identified as the sister species of the Grey Gull (Larus modestus) and the Ross's Gull (Rhodostethia rosea) forms a monophyletic group with the Little Gull (Larus minutus). Our results clearly demonstrate that the genus Larus as currently defined is not monophyletic, since current taxonomy of gulls is based on the use of convergent phenotypic characters. We propose a new systematic arrangement that better reflects their evolutionary history.     

Phylogeny of harvestmen family Gonyleptidae inferred from a multilocus approach (Arachnida: Opiliones)

Gonyleptidae is the second most diverse harvestmen family and the most studied in terms of morphology, behaviour, and ecology. Despite this, few phylogenetic studies have focused on gonyleptids, and those are based on a very limited number of taxa. We addressed this gap by constructing a phylogenetic hypothesis of the family using 101 taxa from all 16 gonyleptid subfamilies and four mitochondrial and nuclear loci (COI, 28S rRNA, 12S rRNA, and 16S rRNA). These were analysed under parsimony and likelihood optimality criteria (and using direct optimization for the former). Relationships among Gonyleptoidea and within each subfamily of Gonyleptidae were largely congruent between parsimony and maximum‐likelihood approaches. Taxonomic actions from our phylogeny include the following: Tricommatidae, new status, is restored as a family; Metasarcidae, new status, is recognized as a family and considered sister to the Cosmetidae; and Cranainae and Manaosbiinae are suggested as members of Gonyleptidae, restoring Roewer's concept of the family. Within Gonyleptidae, the “K92” group—composed of Sodreaninae, Caelopyginae, Hernandariinae, Progonyleptoidellinae, and Gonyleptinae—forms a clade, although the latter two subfamilies are not monophyletic. The genus Parampheres is here transferred to Caelopyginae, and “Multumbo” dimorphicus to Gonyleptinae. Gonyleptidae is characterized by the presence of a ventral process on the penis glans and a bifid apophysis on the male coxa IV. The long‐legged Mitobatinae can be considered monophyletic only if some short‐legged pachylines are included, or if we assume that elongate legs arose twice independently (in the true mitobatine genera and in Longiperna). Pachylinae, the most diverse gonyleptid subfamily, represents several distinct lineages. We further conclude that the traditional use of a small set of morphological characters in the systematics of Gonyleptidae is unable to explain the complex evolution of the family.     

Systematics of North American Froelichia (Amaranthaceae subfam. Gomphrenoideae) II: Phylogeny and biogeographic speciation patterns inferred from nrITS sequence data

Molecular phylogenetic analyses of the nuclear ribosomal DNA internal transcribed spacer (ITS 1 and ITS 2) and the 5.8S gene were used to infer a phylogeny among the ten recognized taxa of Froelichia in North America. Analyses using both maximum parsimony (MP) and maximum-likelihood (ML) depicted a low level of sequence divergence though it was sufficient in most cases to differentiate taxa. Froelichia xantusii, a species restricted to southern Baja California was shown to be the basalmost member of the group subtending three clades. Two of the clades received good bootstrap support in the MP analysis and corresponded to a genetically homogeneous F. interrupta, and a clade comprising the two species F. latifolia and F. texana. A third clade receiving low bootstrap support contained F. floridana, F. gracilis, F. arizonica, and F. drummondii. Species diversity within the genus was centered within the Tamaulipan Brushland region of north-east Mexico and the southern portion of the US state of Texas where taxa from two of the three principal clades occurred, indicating a region of high speciation and diversification within the genus.     

Molecular phylogenetic analysis of Fringillidae, "New World nine-primaried oscines" (Aves: Passeriformes)

Systematic studies of Fringillidae have long been problematic due to their apparent recent and explosive diversification. We present phylogenetic hypotheses of 44 fringillids that represent the overall diversity of the family, based on 3.2 kb of mitochondrial DNA sequences, and phylogenetic analyses for a subset of fringillids based on new and published mitochondrial cytochrome b sequences. Monophyly of Fringillidae and its two constituent subfamilies, Fringillinae and Emberizinae, was consistently supported with the exceptions of Peucedramus being placed outside of Fringillinae and Euphonia being placed within Fringillinae instead of within Emberizinae. Within Emberizinae, Thraupini (tanagers), Cardinalini (cardinals and grosbeaks), and Emberizini (New World sparrows) did not form separate monophyletic groups. Our results indicate that Emberizinae consists of three clades, each with a different overall geographical distribution. Several taxa traditionally considered members of Thraupini fall outside of the thraupine clade, including the only North American genus, Piranga. Consequently, the thraupine clade includes only Neotropical species. Increasing evidence suggests that Fringillidae, often called "New World nine-primaried oscines," does not in fact have a New World origin.     

Origin and diversification of the cryptic ant genus Stenamma Westwood (Hymenoptera: Formicidae), inferred from multilocus molecular data,biogeography and natural history

The genus Stenamma Westwood comprises a group of cryptic, cold tolerant ants that occur throughout the Holarctic and Middle American regions. Traditional approaches to taxonomy and phylogeny are confounded by multiple factors, including the conservative and often convergent morphology of workers and the rarity of reproductive castes in collections. Monophyly of Stenamma and relationships within the genus are uncertain as nearly all previous taxonomic work has been regional in scope. Furthermore, the sister group to Stenamma has not been well established. Here an extensive molecular dataset consisting of ten genes (～8 kb of data), 48 ingroup taxa (20 Nearctic, 6 Palaearctic and 22 Neotropical) and 8 outgroup taxa (6 closely related non‐Stenamma and 2 additional myrmicines) is used to investigate the broad‐scale phylogeny and evolutionary history of Stenamma. Phylogenetic analysis is performed under maximum likelihood and Bayesian frameworks on individual genes and several alternate concatenated datasets, which are used to investigate the effects of inclusion or exclusion of COI and intronic regions. The timing of Stenamma evolution is inferred in beast and ancestral areas are reconstructed using both the s‐diva and DEC methods, as implemented in the programs rasp and lagrange , respectively. Stenamma is revealed as monophyletic with high support and tentatively is sister to a group of New World species placed currently in Aphaenogaster Mayr and Messor Forel. Within Stenamma, two major clades are recovered: a ‘Holarctic clade’ (HOC) and a ‘Middle American clade’ (MAC). The HOC consists of the European S. striatulum Emery sister to two well‐supported groups, the informal ‘debile’ and ‘brevicorne’ clades. The ‘brevicorne’ clade is entirely Nearctic, whereas the ‘debile’ clade includes both Nearctic and Palaearctic representatives. The MAC occurs from the southern United States to northern South America and, with the exception of S. huachucanum Smith, is almost completely isolated geographically from the HOC. It includes a depauperate northern clade and the ‘MAC core’, which is a diverse assemblage of wet forest adapted species found throughout Central America. Divergence dating and biogeographic reconstruction show that Stenamma is most likely to have originated in the Nearctic at the Eocene–Oligocene boundary (～35 Ma) and diversified more rapidly at 16 and 8 Ma for the HOC and MAC, respectively. Potential environmental factors affecting the evolution of Stenamma include the intense global cooling of the late Eocene combined with aridification and mountain building. The phylogenetic results are discussed in relation to the current Stenamma species groups and several new morphological characters are presented to help in identification.