Developmental trait evolution in trilobites

We performed a tree-based analysis of trilobite postembryonic development in a sample of 60 species for which quantitative data on segmentation and growth increments between putative successive instars are available, and that spans much of the temporal, phylogenetic, and habitat range of the group. Three developmental traits were investigated: the developmental mode of trunk segmentation, the average per-molt growth rate, and the conformity to a constant per-molt growth rate (Dyar's rule), for which an original metric was devised. Growth rates are within the normal range with respect to other arthropods and show overall conformity to Dyar's rule. Randomization tests indicate statistically significant phylogenetic signal for growth in early juveniles but not in later stages. Among five evolutionary models fit via maximum likelihood, one in which growth rates vary independently among species, analogous to Brownian motion on a star phylogeny, is the best supported in all ontogenetic stages, although a model with a single, stationary peak to which growth rates are attracted also garners nontrivial support. These results are not consistent with unbounded, Brownian-motion-like evolutionary dynamics, but instead suggest the influence of an adaptive zone. Our results suggest that developmental traits in trilobites were relatively labile during evolutionary history.     

Radiation of pollination systems in the Iridaceae of sub-Saharan Africa

BACKGROUND: Seventeen distinct pollination systems are known for genera of sub-Saharan African Iridaceae and recurrent shifts in pollination system have evolved in those with ten or more species. Pollination by long-tongued anthophorine bees foraging for nectar and coincidentally acquiring pollen on some part of their bodies is the inferred ancestral pollination strategy for most genera of the large subfamilies Iridoideae and Crocoideae and may be ancestral for the latter. Derived strategies include pollination by long-proboscid flies, large butterflies, night-flying hovering and settling moths, hopliine beetles and sunbirds. Bee pollination is diverse, with active pollen collection by female bees occurring in several genera, vibratile systems in a few and non-volatile oil as a reward in one species. Long-proboscid fly pollination, which is apparently restricted to southern Africa, includes four separate syndromes using different sets of flies and plant species in different parts of the subcontinent. Small numbers of species use bibionid flies, short-proboscid flies or wasps for their pollination; only about 2 % of species use multiple pollinators and can be described as generalists. SCOPE: Using pollination observations for 375 species and based on repeated patterns of floral attractants and rewards, we infer pollination mechanisms for an additional 610 species. Matching pollination system to phylogeny or what is known about species relationships based on shared derived features, we infer repeated shifts in pollination system in some genera, as frequently as one shift for every five or six species of southern African Babiana or Gladiolus. Specialized systems using pollinators of one pollination group, or even a single pollinator species are the rule in the family. Shifts in pollination system are more frequent in genera of Crocoideae that have bilaterally symmetric flowers and a perianth tube, features that promote adaptive radiation by facilitating precise shifts in pollen placement, in conjunction with changes in flower colour, scent and tube length. CONCLUSIONS: Diversity of pollination systems explains in part the huge species diversity of Iridaceae in sub-Saharan Africa, and permits species packing locally. Pollination shifts are, however, seen as playing a secondary role in speciation by promoting reproductive isolation in peripheral, ecologically distinct populations in areas of diverse topography, climate and soils. Pollination of Iridaceae in Eurasia and the New World, where the family is also well represented, is poorly studied but appears less diverse, although pollination by both pollen- and oil-collecting bees is frequent and bird pollination rare.     

Convergence and coevolution in a mutualism: evidence from a molecular phylogeny of Ficus

Abstract.— The interaction between Ficus (Moraceae) and their pollinating wasps (Chalcidoidea: Agaonidae; more than 700 species-specific couples) is one of the most specialized mutualisms found in nature. Both partners of this interaction show extensive variation in their respective biology. Here we investigate Ficus life-history trait evolution and fig/fig wasp coadaptation in the context of a well-resolved molecular phylogeny. Mapping out variations in Ficus life-history traits on an independently derived phylogeny constructed from ribosomal DNA sequences (external and internal transcribed spacer) reveals several parallel transitions in Ficus growth habit and breeding system. Convergent trait evolution might explain the discrepancies between morphological analyses and our molecular reconstruction of the genus. Morphological characters probably correlate with growth habit and breeding system and could therefore be subject to convergent evolution. Furthermore, we reconstruct the evolution of Ficus inflorescence characters that are considered adaptations to the pollinators. Our phylogeny reveals convergences in ostiole shape, stigma morphology, and stamen:ovule ratio. Statistical tests taking into account the phylogenetic relationship of the species show that transitions in ostiole shape are correlated with variation in wasp pollinator head shape, and evolutionary changes in stigma morphology and stamen:ovule ratio correlate with changes in the pollination behavior of the associated wasp. These correlations provide evidence for reciprocal adaptations of morphological characters between these mutualistic partners that have interacted over a long evolutionary time. In light of previous ecological studies on mutualism, we discuss the adaptive significance of these correlations and what they can tell us about the coevolutionary process occurring between figs and their pollinators.     

The evolution of Cayaponia (Cucurbitaceae): Repeated shifts from bat to bee pollination and long-distance dispersal to Africa 2-5 million years ago

? Premise of the study: The Cucurbitaceae genus Cayaponia comprises ～60 species that occur from Uruguay to the southern United States and the Caribbean; C. africana occurs in West Africa and on Madagascar. Pollination is by bees or bats, raising the question of the evolutionary direction and frequency of pollinator shifts. Studies that investigated such shifts in other clades have suggested that bat pollination might be an evolutionary end point. ? Methods: Plastid and nuclear DNA sequences were obtained for 50 accessions representing 30 species of Cayaponia and close relatives, and analyses were carried out to test monophyly, infer divergence times, and reconstruct ancestral states for habitat preferences and pollination modes. ? Key results: The phylogeny shows that Cayaponia is monophyletic as long as Selysia (a genus with four species from Central and South America) is included. The required nomenclatural transfers are made in this paper. African and Madagascan accessions of C. africana form a clade that is part of a polytomy with Caribbean and South American species, and the inferred divergence time of 2-5 Ma implies a transoceanic dispersal event from the New World to Africa. The ancestral state reconstructions suggest that Cayaponia originated in tropical forests from where open savannas were reached several times and that bee pollination arose from bat pollination, roughly concomitant with the shifts from forests to savanna habitats. ? Conclusions: Cayaponia provides the first example of evolutionary transitions from bat to bee pollination as well as another instance of transoceanic dispersal from the New World to Africa.     

CONVERGENT AND CORRELATED EVOLUTION OF MAJOR LIFE‐HISTORY TRAITS IN THE ANGIOSPERM GENUS LEUCADENDRON (PROTEACEAE)

Natural selection is expected to cause convergence of life histories among taxa as well as correlated evolution of different life‐history traits. Here, we quantify the extent of convergence of five key life‐history traits (adult fire survival, seed storage, degree of sexual dimorphism, pollination mode, and seed‐dispersal mode) and test hypotheses about their correlated evolution in the genus Leucadendron (Proteaceae) from the fire‐prone South African fynbos. We reconstructed a new molecular phylogeny of this highly diverse genus that involves more taxa and molecular markers than previously. This reconstruction identifies new clades that were not detected by previous molecular study and morphological classifications. Using this new phylogeny and robust methods that account for phylogenetic uncertainty, we show that the five life‐history traits studied were labile during the evolutionary history of the genus. This diversity allowed us to tackle major questions about the correlated evolution of life‐history strategies. We found that species with longer seed‐dispersal distances tended to evolve lower pollen‐dispersal distance, that insect‐pollinated species evolved decreased sexual dimorphism, and that species with a persistent soil seed‐bank evolved toward reduced fire‐survival ability of adults.     

Correlations of Life Form,Pollination Mode and Sexual System in Aquatic Angiosperms

Aquatic plants are phylogenetically well dispersed across the angiosperms. Reproductive and other life-history traits of aquatic angiosperms are closely associated with specific growth forms. Hydrophilous pollination exhibits notable examples of convergent evolution in angiosperm reproductive structures, and hydrophiles exhibit great diversity in sexual system. In this study, we reconstructed ancestral characters of aquatic lineages based on the phylogeny of aquatic angiosperms. Our aim is to find the correlations of life form, pollination mode and sexual system in aquatic angiosperms. Hydrophily is the adaptive evolution of completely submersed angiosperms to aquatic habitats. Hydroautogamy and maleflower-ephydrophily are the transitional stages from anemophily and entomophily to hydrophily. True hydrophily occurs in 18 submersed angiosperm genera, which is associated with an unusually high incidence of unisexual flowers. All marine angiosperms are submersed, hydrophilous species. This study would help us understand the evolution of hydrophilous pollination and its correlations with life form and sexual system.     

Phylogeny of the tribe Fumarieae (Papaveraceae s.l.) based on chloroplast and nuclear DNA sequences: Evolutionary and biogeographic implications

? Premise of the Study: Little research has been done at the molecular level on the tribe Fumarieae (Papaveraceae). Papaveraceae is a model plant group for studying evolutionary patterns despite the lack of a reference phylogeny for this tribe. We investigated the phylogenetic relationships within the tribe to complete the molecular data for this family in order to help understand its character evolution and biogeographic pattern. ? Methods: We used maximum-parsimony and Bayesian approaches to analyze five DNA regions for 25 species representing 10 of the 11 Fumarieae genera and five outgroups. Evolutionary pathways of four characters (habit, life span, type of fruit, and number of seeds per fruit) were inferred on the phylogeny using parsimony. The ancestral distribution areas were reconstructed using dispersal-vicariance analysis. ? Key Results: Fumarieae is monophyletic and includes three groups that agree with the morphology-based subtribes: Discocapninae, Fumariinae, and Sarcocapninae. Within subtribes, the relationships among genera were different from those obtained with morphological data. Annual life span, nonchasmophytic habit, and a several-seeded capsule were the basal character states for the tribe. The ancestor occupied a continuous area between West Eurasia and Africa. Vicariances explain the divergence between lineages Discocapninae (South Africa) and Fumariinae-Sarcocapninae (Mediterranean), and the disjunction of Fumariinae (Mediterranean-Central Asia). ? Conclusions: Molecular phylogeny confirms the subtribal classification of Fumarieae based on morphology. However it provides different results regarding the relationships among genera within each subtribe, which affects the inference of the evolutionary pathway followed by the four selected characters. The disjunct distribution of the tribe is explained by different vicariance scenarios.     

Ancestral reconstruction of flower morphology and pollination systems in Schizanthus (Solanaceae)

Concerted changes in flower morphology and pollinators provide strong evidence on adaptive evolution. Schizanthus (Solanaceae) has zygomorphic flowers and consists of 12 species of annual or biennial herbs that are distributed mainly in Chile and characterized by bee-, hummingbird-, and moth-pollination syndromes. To infer whether flowers diversified in relation to pollinator shifts, we traced the evolutionary trajectory of flower traits and visitors onto a phylogeny based on sequence data from ITS, waxy, and trnF/ndhJ DNA. Maximum-likelihood ancestral reconstruction of floral traits suggests that ancestral Schizanthus had a bee-pollination syndrome. The hummingbird syndrome evolved in S. grahamii, a high elevation species in the Andes. The moth syndrome evolved in the ancestor of three species that inhabit the Atacama Desert. Results of mapping flower visitors onto the phylogeny show that the shift from bee to hummingbird pollination concurred with a shift in pollinators as predicted by the syndromes. However, the same pattern was not found for the moth syndrome. Visits by moths were observed only in one of the three moth-syndrome species, and at a very low rate. This mismatch suggests either anachronic floral characters or maintenance of rare, imperceptible moth pollination backed up by capacity for autonomous selfing. Overall, results suggest that diversification of flower traits in Schizanthus has occurred in relation to pollinator shifts.     

Molecular phylogenetics of Houstonia (Rubiaceae): descending aneuploidy and breeding system evolution in the radiation of the lineage across North America

Nuclear and chloroplast DNA sequence variation was used to infer evolutionary relationships within and among members of Houstonia (Rubiaceae) and other closely related genera in North America. Sequences from the internal transcribed spacer (ITS) of the nrDNA and a cpDNA intron in the trnL gene were used to reconstruct phylogenetic relationships of 30 species of Houstonia and closely related genera. The data suggest that the North American species of Houstonia are not monophyletic, but belong to the same lineage as Stenaria. The radiation of this lineage has been accompanied by changes in the basic chromosome number of the major clades through descending aneuploidy. This loss of chromosomes was also associated with northward colonization of North America. However, other characters, such as an annual versus perennial habit, heterostylous and homostylous breeding systems, and the evolution of self fertilization, seem to be labile throughout the lineage, originating multiple times throughout the evolutionary history of the lineage.     

PHYLOGENETIC ANALYSIS OF TRAIT EVOLUTION AND SPECIES DIVERSITY VARIATION AMONG ANGIOSPERM FAMILIES

Angiosperm families differ greatly from one another in species richness (S). Previous studies have attributed significant components of this variation to the influence of pollination mode (biotic/abiotic) and growth form (herbaceous/woody) on speciation rate, but these results suffer difficulties of interpretation because all the studies ignored the phylogenetic relationships among families. We use a molecular phylogeny of the angiosperm families to reanalyse correlations between S and family-level traits and use reconstructions of trait evolution to interpret the results. We confirm that pollination mode and growth form are correlated with S and show that the majority of changes in pollination mode involved a change from biotic to abiotic pollination with an associated fall in speciation rate. The majority of growth form changes involved the evolution of herbaceousness from woodiness with a correlated rise in speciation rate. We test the hypothesis of Ricklefs and Renner (1994) that “evolutionary flexibility” rather than other trait changes triggered increased speciation rates in some families, but find little support for the hypothesis.     

Species diversity and ecological range in relation to ploidy level in the flora of the Pyrenees

Polyploidy is a major process in plant evolution. Surprisingly, no study has examined its role in species diversification and ecological distribution in relation to other life history traits. In this study, we examine to what extent polyploidy and the other traditionally examined biological traits (pollination mode, dispersal mode and growth form) account for ecological and taxonomic diversity in the flora of the Pyrenees. Fifty genera (in 22 angiosperm families) were classified according to ploidy level, growth form, pollination mode and dispersal mode, and 451 species and/or subspecies in these 50 genera were classified according to ploidy level and growth form. We examined the contribution of ploidy level, pollination and dispersal modes and growth form to (i) the ecological range of species and genera, i.e., the number of natural habitats (defined by a combination of ecological characteristics) where they occur, and (ii) the taxonomic diversity of the 50 genera. Ploidy level and dispersal mode had significant effects on the taxonomic diversity of the 50 genera. Taxonomic diversity, but not polyploidy per se, was significantly correlated with ecological range of genera. For individual species, diploids had a larger ecological range than polyploids, and herbaceous growth forms had wider ecological distributions than other growth forms. Our results indicate that polyploidisation may be a source of ecological diversification of genera, not by increasing the ecological range of particular polyploid species compared to diploids, but rather by creating taxonomic diversity that leads in some genera to a diversification of the habitats occupied by different ploidy levels. This observation is consistent with previous observations of ecological divergence of chromosomal races in some species in the Alps and in the Pyrenees. As found in other studies, species diversification in the studied flora appears to be greatly influenced by the occurrence of multiple dispersal modes, while ecological range of species or subspecies is significantly increased by the presence of herbaceous species.     

Molecular evolution, adaptive radiation, and geographic diversification in the amphiatlantic family Rapateaceae: evidence from ndhF sequences and morphology

Rapateaceae (16 genera, approximately 100 species) is largely restricted to the tepuis and sandplains of the Guayana Shield in northern South America, with Maschalocephalus endemic to West Africa. The family has undergone extensive radiation in flower form, leaf shape, habit, and habitat. To analyze the evolution of these distributions and traits, we derived a molecular phylogeny for representatives of 14 genera, based on sequence variation in the chloroplast-encoded ndhF gene. The lowland subfamily Rapateoideae is paraphyletic and includes the largely montane subfamily Saxofridericioideae as a monophyletic subset. Overall, the morphological/anatomical data differ significantly from ndhF sequences in phylogenetic structure, but show a high degree of concordance with the molecular tree in three of four tribes. Branch lengths are consistent with the operation of a molecular clock. Maschalocephalus diverges only slightly from other Monotremae: it is the product of relatively recent, long-distance dispersal, not continental drift--only its habitat atop rifted, nutrient-poor sandstones is vicariant. The family appears to have originated approximately 65 Mya in inundated lowlands of the Guayana Shield, followed by: (1) wide geographic spread of lowland taxa along riverine corridors; (2) colonization of Amazonian white-sand savannas in the western Shield; (3) invasion of tepui habitats with frequent speciation, evolution of narrow endemism, and origin of hummingbird pollination in the western Shield; and (4) reinvasion of lowland white-sand savannas. The apparent timing of speciation in the Stegolepis alliance about 6-12 Mya occurred long after the tepuis began to be dissected from each other as the Atlantic rifted approximately 90 Mya. Given the narrow distributions of most montane taxa, this suggests that infrequent long-distance dispersal combined with vicariance accounts for speciation atop tepuis in the Stegolepis alliance.     

Using a mega-phylogeny of seed plants to test for non-random patterns of areal-types across the Chinese tree of life

The species composition of plant assemblages can in large part be explained by a long history of biogeographic and evolutionary events. Over the past decade, botanists and plant ecologists have increasingly sought to quantify phylogenetic signal in ecological traits to help inform their inferences regarding the mechanisms driving plant assemblages. However, most studies with a test of phylogenetic signal in the ecological traits have focused on a local scale, while comparatively few studies have been carried out on a regional scale. In this study, I presented a family-level phylogeny and a genus-level phylogeny that included all families and genera of extant seed plants in China, and use both phylogenies to examine whether areal-types or distribution patterns of families and genera of seed plants are non-randomly distributed across the Chinese tree of life. My study shows that the areal-types of families and genera of seed plants exhibit significant phylogenetic signal across the family- or genus-level phylogeny of seed plants in China.     

Phylogeny and radiation of pollination systems in DISA (Orchidaceae)

We studied the patterns of adaptive radiation in Disa, a large orchid genus in southern Africa. A cladogram for 27 species was constructed using 44 morphological characters. Pollination systems were then mapped onto the phylogeny in order to analyze pathways of floral evolution. Shifts from one pollination system to another have been a major feature of the evolutionary diversification of Disa. Unlike many plant genera that are pollinated mainly by a single group of insects, radiation in Disa has encompassed nearly all major groups of pollinating insects; in all, 19 different specialized pollination systems have been found in the 27 species included in this analysis. Another striking pattern is the repeated evolution of broadly similar pollination systems in unrelated clades. For example, butterfly-pollinated flowers have evolved twice; showy deceptive flowers pollinated by carpenter bees, twice; long-spurred flowers pollinated by long-tongued flies, four times; night-scented flowers pollinated by moths, three times; and self-pollination, three times. This suggests that a few dominant pollinator species in a region may be sufficient to generate diversification in plants through repeated floral shifts that never retrace the same pathways.     

Pollination mode in fig wasps: the predictive power of correlated traits

The over 700 species of Ficus are thought to have co-speciated with their obligate pollinators (family Agaonidae). Some of these wasp species pollinate figs actively, while others are passive pollinators. Based on direct observations of mode of pollination in 88 species, we show that mode of pollination can confidently be predicted from fig traits only (anther-to-ovule ratio) or from wasp traits only (presence of coxal combs). The presence of pollen pockets is not a predictor of mode of pollination. Data, direct and indirect, on 142 species, demonstrate numerous cases of the loss of active pollination and suggest one or few origins of active pollination. Hence, active pollination, an impressive example of the sophisticated traits that may result from mutualistic coevolution, depends on selective forces that can be overcome in some species, allowing reversions. Despite frequent loss, active pollination remains the predominant mode of pollination in Ficus.     

A molecular phylogeny and classification of Verbenaceae

? Premise of the study: Verbenaceae consist of trees, shrubs, lianas, and herbs distributed primarily in Latin America, where they occur in a wide array of ecosystems. A second center of diversity exists in Africa. Competing morphology-based classifications that rely on different traits conflict in significant ways. A broad phylogenetic study was undertaken to assess those classifications and to examine the historical geography of the family. ? Methods: Analysis of seven chloroplast DNA regions for 109 species, representing all genera except one monotypic genus, provide inference into evolutionary relationships in Verbenaceae. ? Key results: The phylogeny shows that none of the traditional classifications reflect phylogenetic relationships very well. Eight clades are recognized as tribes (Casselieae, Citharexyleae, Duranteae, Lantaneae, Neospartoneae trib. nov., Petreeae, Priveae, and Verbeneae). Two genera, Dipyrena and Rhaphithamnus, remain unplaced in these larger clades. Petreeae, which consist of Neotropical lianas, are sister to the rest of the family. Lantaneae and Verbeneae together form a derived clade that comprises approximately two-thirds of the species in Verbenaceae. ? Conclusions: We present a new tribal classification, including one new tribe, Neospartoneae trib. nov., to accommodate three small genera of Argentine species (Diostea, Neosparton, and Lampaya). Phylogenetic inference suggests a South American origin for Verbenaceae, with approximately six colonization events having given rise to the Old World species.     

Spatiotemporal Evolution of the Global Species Diversity of Rhododendron

Evolutionary radiation is a widely recognized mode of species diversification, but its underlying mechanisms have not been unambiguously resolved for species-rich cosmopolitan plant genera. In particular, it remains largely unknown how biological and environmental factors have jointly driven its occurrence in specific regions. Here, we use Rhododendron, the largest genus of woody plants in the Northern Hemisphere, to investigate how geographic and climatic factors, as well as functional traits, worked together to trigger plant evolutionary radiations and shape the global patterns of species richness based on a solid species phylogeny. Using 3,437 orthologous nuclear genes, we reconstructed the first highly supported and dated backbone phylogeny of Rhododendron comprising 200 species that represent all subgenera, sections, and nearly all multispecies subsections, and found that most extant species originated by evolutionary radiations when the genus migrated southward from circumboreal areas to tropical/subtropical mountains, showing rapid increases of both net diversification rate and evolutionary rate of environmental factors in the Miocene. We also found that the geographically uneven diversification of Rhododendron led to a much higher diversity in Asia than in other continents, which was mainly driven by two environmental variables, that is, elevation range and annual precipitation, and were further strengthened by the adaptation of leaf functional traits. Our study provides a good example of integrating phylogenomic and ecological analyses in deciphering the mechanisms of plant evolutionary radiations, and sheds new light on how the intensification of the Asian monsoon has driven evolutionary radiations in large plant genera of the Himalaya-Hengduan Mountains.     

Rush hour at the Museum – Diversification patterns provide new clues for the success of figs (Ficus L., Moraceae)

Tropical rainforests harbour much of the earth's plant diversity but little is still known about how it evolved and why a small number of plant genera account for the majority. Whether this success is due to rapid turnover or constant evolution for these hyper-diverse plant genera is here tested for the species-rich genus Ficus L. (figs). The pan-tropical distribution of figs makes it an ideal study group to investigate rainforest hyper-diversification patterns. Using a recently published, dated and comprehensive phylogenetic hypothesis, we infer that figs are an old lineage that gradually accumulated species and exhibits very low extinction rates, which corresponds to the ‘museum model’ of evolution. Overall, no major significant shifts in evolutionary dynamics are detected, yet two shifts with lower probability are found. Hemi-epiphytism, monoecy, and active pollination are traits that possibly are associated with the hyper-diversity found in figs, making it possible for the plants to occupy new niches followed by extensive radiation over evolutionary time scales. Figs possess unique diversification patterns compared to other typical rainforest genera.     

Phylogenetic analysis of the ecological correlates of dioecy in angiosperms

We report on a phylogenetic analysis of correlations between the occurrence of dioecy and several ecological and life-history attributes: tropical distribution, woody growth form, abiotic pollination, small inconspicuous flowers and inflorescences, many-flowered inflorescences and fleshy fruits. Various hypotheses have been proposed to explain why associations occur between dioecy and several of these attributes, yet most assume that dioecy originates more often in clades with these traits than in clades with alternative character states. To investigate correlations between dioecy and these attributes, and to provide insights into the potential evolutionary pathways that have led to these associations, we assigned states of these traits to genera on a large-scale molecular phylogeny of the angiosperms; we then used maximum-likelihood analysis to analyse the presence of correlations and the sequence of acquisition of traits. Phylogenetic analysis revealed correlations between dioecy and six of the seven attributes; only many-flowered inflorescences exhibiting no association with the dioecious condition. The particular correlations that were revealed and the strength of the association differed among the three main monophyletic groups of angiosperms (Rosids, Asterids, and Eumagnoliids). Our analysis provided no general support for the hypothesis that dioecy is more likely to evolve in lineages already possessing the seven attributes we considered. Further analysis of the intercorrelations of the seven attributes provided evidence for non-independence between some of the traits, implying that functional associations among these traits have influenced the ecology and evolution of dioecious species.     

A comparative analysis of Y chromosome and mtDNA phylogenies of the Hylobates gibbons

ABSTRACT: BACKGROUND: The evolutionary relationships of closely related species have long been of interest to biologists since these species experienced different evolutionary processes in a relatively short period of time. Comparison of phylogenies inferred from DNA sequences with differing inheritance patterns, such as mitochondrial, autosomal, and X and Y chromosomal loci, can provide more comprehensive inferences of the evolutionary histories of species. Gibbons, especially the genus Hylobates, are particularly intriguing as they consist of multiple closely related species which emerged rapidly and live in close geographic proximity. Our current understanding of relationships among Hylobates species is largely based on data from the maternally-inherited mitochondrial DNAs (mtDNAs). RESULTS: To infer the paternal histories of gibbon taxa, we sequenced multiple Y chromosomal loci from 26 gibbons representing 10 species. As expected, we find levels of sequence variation some five times lower than observed for the mitochondrial genome (mtgenome). Although our Y chromosome phylogenetic tree shows relatively low resolution compared to the mtgenome tree, our results are consistent with the monophyly of gibbon genera suggested by the mtgenome tree. In a comparison of the molecular dating of divergences and on the branching patterns of phylogeny trees between mtgenome and Y chromosome data, we found: 1) the inferred divergence estimates were more recent for the Y chromosome than for the mtgenome, 2) the species H. lar and H. pileatus are reciprocally monophyletic in the mtgenome phylogeny but a H. pileatus individual falls into the H. lar Y chromosome clade. CONCLUSIONS: Based on the ~6.4 kb of Y chromosomal DNA sequence data generated for each of the 26 individuals in this study, we provide molecular inferences on gibbon and particularly on Hylobates evolution complementary to those from mtDNA data. Overall, our results illustrate the utility of comparative studies of loci with different inheritance patterns for investigating potential sex specific processes on the evolutionary histories of closely related taxa, and emphasize the need for further sampling of gibbons of known provenance.