Evolution of the latitudinal diversity gradient in the hyperdiverse ant genus Pheidole

AimThe latitudinal diversity gradient is the dominant geographic pattern of life on Earth, but a consensus understanding of its origins has remained elusive. The analysis of recently diverged, hyperâ rich invertebrate groups provides an opportunity to investigate latitudinal patterns with the statistical power of large trees while minimizing potentially confounding variation in ecology and history. Here, we synthesize global phylogenetic and macroecological data on a hyperdiverse (> 1,100 species) ant radiation, Pheidole and test predictions of three general explanations for the latitudinal gradient: variation in diversification rates, tropical conservatism and ecological regulation.LocationGlobal.Time periodThe past 35 million years.Major taxa studiedThe hyperdiverse ant genus Pheidole Westwood.MethodsWe assembled geographic data for 1,499 species and morphospecies, and inferred a dated phylogeny for 449 species of Pheidole, including 167 species newly sequenced for this study. We tested for correlations between diversification rate and latitude with Bayesian analysis of macroevolutionary mixtures (BAMM), hidden state speciation and extinction (HiSSE), geographic state speciation and extinction (GeoSSE), and a nonâ parametric method (FiSSE), evaluated evidence for richness steady state, and examined patterns of diversification as Pheidole spread around the globe.ResultsThere was no evidence of systematic variation of net diversification rates with latitude across any of the methods. We found that Pheidole diversification occurred in bursts when new continents were colonized, followed by a slowdown in each region, but there is no evidence richness has saturated at an equilibrium in any region. Additionally, we found latitudinal affinity is moderately conserved with a Neotropical ancestor and simulations show that phylogenetic inertia alone is sufficient to produce the gradient pattern.Main conclusionsOur results provide no evidence that diversification rates vary systematically with latitude. Richness is far from steady state in each region, contrary to the ecological regulation hypothesis, although there is evidence that ecological opportunity promotes diversification after colonization of new areas. The fact that niche conservatism is strong enough to produce the gradient pattern is in accord with the tropical conservatism hypothesis. Overall, these results shed light on the mechanisms underlying the emergence of the diversity gradient within the past 34 million years, complementing recent work on deeper timeâ scales, and more generally contribute toward muchâ needed invertebrate perspective on global biodiversity dynamics.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148253/1/geb12867-sup-0001-AppendixS1-S2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148253/2/geb12867-sup-0005-TableS3.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148253/3/geb12867-sup-0006-Supinfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148253/4/geb12867-sup-0002-FigS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148253/5/geb12867.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148253/6/geb12867_am.pd

Molecular phylogeny of Indo‐Pacific carpenter ants (Hymenoptera: Formicidae, Camponotus) reveals waves of dispersal and colonization from diverse source areas

Ants that resemble Camponotus maculatus (Fabricius, 1782) present an opportunity to test the hypothesis that the origin of the Pacific island fauna was primarily New Guinea, the Philippines, and the Indo‐Malay archipelago (collectively known as Malesia). We sequenced two mitochondrial and four nuclear markers from 146 specimens from Pacific islands, Australia, and Malesia. We also added 211 specimens representing a larger worldwide sample and performed a series of phylogenetic analyses and ancestral area reconstructions. Results indicate that the Pacific members of this group comprise several robust clades that have distinctly different biogeographical histories, and they suggest an important role for Australia as a source of Pacific colonizations. Malesian areas were recovered mostly in derived positions, and one lineage appears to be Neotropical. Phylogenetic hypotheses indicate that the orange, pan‐Pacific form commonly identified as C. chloroticus Emery 1897 actually consists of two distantly related lineages. Also, the lineage on Hawaiʻi, which has been called C. variegatus (Smith, 1858), appears to be closely related to C. tortuganus Emery, 1895 in Florida and other lineages in the New World. In Micronesia and Polynesia the C. chloroticus‐like species support predictions of the taxon‐cycle hypothesis and could be candidates for human‐mediated dispersal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112260/1/cla12099-sup-0002-FigureS2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112260/2/cla12099-sup-0003-FigureS3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112260/3/cla12099-sup-0001-FigureS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112260/4/cla12099-sup-0004-FigureS4.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112260/5/cla12099-sup-0005-FigureS5.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112260/6/cla12099-sup-0006-FigureS6.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112260/7/cla12099.pd

Colonize, radiate, decline: Unraveling the dynamics of island community assembly with Fijian trap‐jaw ants

The study of island community assembly has been fertile ground for developing and testing theoretical ideas in ecology and evolution. The ecoevolutionary trajectory of lineages after colonization has been a particular interest, as this is a key component of understanding community assembly. In this system, existing ideas, such as the taxon cycle, posit that lineages pass through a regular sequence of ecoevolutionary changes after colonization, with lineages shifting toward reduced dispersal ability, increased ecological specialization, and declines in abundance. However, these predictions have historically been difficult to test. Here, we integrate phylogenomics, population genomics, and X-ray microtomography/3D morphometrics, to test hypotheses for whether the ecomorphological diversity of trap-jaw ants (Strumigenys) in the Fijian archipelago is assembled primarily through colonization or postcolonization radiation, and whether species show ecological shifts toward niche specialization, toward upland habitats, and decline in abundance after colonization. We infer that most Fijian endemic Strumigenys evolved in situ from a single colonization and have diversified to fill a large fraction of global morphospace occupied by the genus. Within this adaptive radiation, lineages trend to different degrees toward high elevation, reduced dispersal ability, and demographic decline, and we find no evidence of repeated colonization that displaces the initial radiation. Overall these results are only partially consistent with taxon cycle and associated ideas, while highlighting the potential role of priority effects in assembling island communities

An ant genus-group ( Prenolepis ) illuminates the biogeography and drivers of insect diversification in the Indo-Pacific

The Malay Archipelago and the tropical South Pacific (hereafter the Indo-Pacific region) are considered biodiversity hotspots, yet a general understanding of the origins and diversification of species-rich groups in the region remains elusive. We aimed to test hypotheses for the evolutionary processes driving insect species diversity in the Indo-Pacific using a higher-level and comprehensive phylogenetic hypothesis for an ant clade consisting of seven genera. We estimated divergence times and reconstructed the biogeographical history of ant species in the Prenolepis genus-group (Formicidae: Formicinae: Lasiini). We used a fossil-calibrated phylogeny to infer ancestral geographical ranges utilizing a biogeographic model that includes founder-event speciation. Ancestral state reconstructions of the ants\u27 ecological preferences, and diversification rates were estimated for selected Indo-Pacific clades. Overall, we report that faunal interchange between Asia and Australia has occurred since at least 20–25 Ma, and early dispersal to the Fijian Basin happened during the early and mid-Miocene (ca. 10–20 Ma). Differences in diversification rates across Indo-Pacific clades may be related to ecological preference breadth, which in turn may have facilitated geographical range expansions. Ancient dispersal routes suggested by our results agree with the palaeogeography of the region. For this particular group of ants, the rapid orogenesis in New Guinea and possibly subsequent ecological shifts may have promoted their rapid diversification and widespread distribution across the Indo-Pacific

The ants [Hymenoptera: Formicidae] of Fiji: Systematics, biogeography and conservation of an island arc fauna

This study examines the taxonomy, systematics and biogeographic history of the remarkable ant [Hymenoptera: Formicidae] fauna of the Fiji Islands. Chapter One is a synoptic revision of the Fijian ant fauna with a background of the archipelago's geologic history. A total of 186 species representing 42 genera are recognized. Of these species, 68% are endemic to Fiji, 16% are native to the Pacific region, and 12% are introduced into the Pacific region. Taxonomic synopses of each species, keys to most genera, and a species list are given. Chapters Two and Three are detailed studies of the taxonomy, phylogeny, biogeography and conservation of two of the many ant genera that have diversified into endemic radiations within the archipelago. Chapter Two examines the 11 species of Fijian Lordomyrma [Formicidae: Myrmicinae], five of which are described as new. Descriptions of each species are provided, along with distribution maps, images, and a key to workers. The phylogeny of the Fijian taxa and their congeners from across the Pacific is inferred by analyzing the fragments of four nuclear genes 28S, argK, LW Rh, CAD) in order to test alternative hypothesis concerning their taxonomic and biogeographic history. The Fijian Lordomyrma are found to be a monophyletic lineage that split from a sister group in Papua New Guinea approximately 8.8 million years ago (Ma). Chapter Three examines the seven species of the spinescent Pheidole roosevelti group [Formicidae: Myrmicinae], five of which are described as new. Descriptions of each species are provided, along with distribution maps, images, and a key for the identification of workers, majors and queens. The phylogeny of the group, along with congeners from Fiji and across the Pacific, is inferred using two mitochondrial genes (COI, cytb) and two nuclear genes (H3, EF1α-F2) from 66 taxa in order to test whether the aberrant spine morphology was inherited from congeners in the subgenus Pheidolacanthinus. The group is monophyletic, and the modern-day clade is estimated to have diverged approximately 7.4–12.2 Ma. The group is more closely related to Fijian Pheidole of conservative morphology than to any Pheidola-canthinus species, suggesting independent acquisition of the spinescent morphology

The Ants of Fiji

The ant fauna of the Fijian archipelago is a diverse assemblage of endemic radiations, pan-Pacific species, and exotics introduced from around the world. Here we provide a taxonomic synopsis of the entire Fijian ant fauna by incorporating previously published information with the results of a recently completed, archipelago-wide biodiversity inventory. This synopsis updates the first and only other treatment of the fauna, W. M. Mann’s 1921 monograph, The Ants of the Fiji Islands. A total of 187 ant species representing 43 genera are recognized here. Of these species, 88% are native to the Pacific region, 70% are endemic to Fiji, and 12% are introduced into the Pacific region. Approximately 45 ant species in Fiji are undescribed, and are identified here by assigned code names. An illustrated key to genera, synopses of each species, keys to species of all genera, and a species list is provided. The work is further illustrated with specimen images, distribution maps, and habitat-elevation charts for all species. Seven taxa are promoted to full species status: Camponotus fijianus Özdikmen, stat. n., Camponotus kadi Mann stat. n., C. levuanus Mann stat. n., C. sadinus Mann stat. n., C. umbratilis Wheeler stat.n., Poecilomyrma myrmecodiae Mann stat. n., Romblonella liogaster (Santschi) stat. n. The following five taxa are revived from synonymy: Hypoponera eutrepta (Wilson) stat. rev., H. vitiensis (Mann) stat. rev., Monomorium vitiense (Mann) stat. rev., Paraparatrechina oceanica (Mann) stat. rev., N. vitiensis (Mann) stat. rev. The following new synonymies are proposed (senior synonym listed first): Camponotus cristatus Mann = C. cristatus nagasau Mann; C. kadi Mann = C. loloma Mann = C. trotteri Mann; C. polynesicus Emery = C. maudella Mann = C. maudella seemanni Mann = C. janussus Bolton; Pheidole knowlesi Mann = P. extensa Mann; Philidris nagasau (Mann) = P. alticola (Mann) = P. agnatus (Mann); Romblonella liogaster (Santschi) = R. vitiensis Smith, M. Lectotypes are designated for the following species: Camponotus vitiensis Mann, Gnamptogenys aterrima (Mann), Poecilomyrma senirewae Mann

New species of Lordomyrma (Hymenoptera: Formicidae) from Southeast Asia and Fiji

Lucky, Andrea, Sarnat, Eli M. (2008): New species of Lordomyrma (Hymenoptera: Formicidae) from Southeast Asia and Fiji. Zootaxa 1681: 37-46, DOI: 10.5281/zenodo.18040

Pheidole wilsoni major worker (CASENT0184311)

Original scan files (dicom format) of Pheidole wilsoni major worker CASENT018431

Revision of the ant genus Proceratium Roger (Hymenoptera, Proceratiinae) in Fiji

The Fiji archipelago harbours a surprisingly diverse and endemic ant fauna, despite its isolated and remote location in the South Pacific. The ant genus Proceratium is present on Fiji with three endemic species, of which P. oceanicum De Andrade, 2003 and P. relictum Mann, 1921 were previously known. In this study we describe the third species: P. vinaka sp. n. All three species are members of the widespread and species-rich P. silaceum clade. In order to integrate the new species into the current taxonomic system, we present an illustrated identification key to the worker caste of the three Fijian species. In addition, we provide a detailed description of P. vinaka, as well as species accounts for the other two species, which include diagnoses, taxonomic discussions, specimen photographs, and a distribution map