A Mid-Cretaceous Origin of Sociality in Xylocopine Bees with Only Two Origins of True Worker Castes Indicates Severe Barriers to Eusociality

The origin of sterile worker castes, resulting in eusociality, represents one of the major evolutionary transitions in the history of life. Understanding how eusociality has evolved is therefore an important issue for understanding life on earth. Here we show that in the large bee subfamily Xylocopinae, a simple form of sociality was present in the ancestral lineage and there have been at least four reversions to purely solitary nesting. The ancestral form of sociality did not involve morphological worker castes and maximum colony sizes were very small. True worker castes, entailing a life-time commitment to non-reproductive roles, have evolved only twice, and only one of these resulted in discrete queen-worker morphologies. Our results indicate extremely high barriers to the evolution of eusociality. Its origins are likely to have required very unusual life-history and ecological circumstances, rather than the amount of time that selection can operate on more simple forms of sociality

Evolution of Blind Beetles in Isolated Aquifers: A Test of Alternative Modes of Speciation

Evidence is growing that not only allopatric but also sympatric speciation can be important in the evolution of species. Sympatric speciation has most convincingly been demonstrated in laboratory experiments with bacteria, but field-based evidence is limited to a few cases. The recently discovered plethora of subterranean diving beetle species in isolated aquifers in the arid interior of Australia offers a unique opportunity to evaluate alternative modes of speciation. This naturally replicated evolutionary experiment started 10-5 million years ago, when climate change forced the surface species to occupy geographically isolated subterranean aquifers. Using phylogenetic analysis, we determine the frequency of aquifers containing closely related sister species. By comparing observed frequencies with predictions from different statistical models, we show that it is very unlikely that the high number of sympatrically occurring sister species can be explained by a combination of allopatric evolution and repeated colonisations alone. Thus, diversification has occurred within the aquifers and likely involved sympatric, parapatric and/or microallopatric speciation

The Evolution of Functionally Redundant Species; Evidence from Beetles

While species fulfill many different roles in ecosystems, it has been suggested that numerous species might actually share the same function in a near neutral way. So-far, however, it is unclear whether such functional redundancy really exists. We scrutinize this question using extensive data on the world’s 4168 species of diving beetles. We show that across the globe these animals have evolved towards a small number of regularly-spaced body sizes, and that locally co-existing species are either very similar in size or differ by at least 35%. Surprisingly, intermediate size differences (10–20%) are rare. As body-size strongly reflects functional aspects such as the food that these generalist predators can eat, these beetles thus form relatively distinct groups of functional look-a-likes. The striking global regularity of these patterns support the idea that a self-organizing process drives such species-rich groups to self-organize evolutionary into clusters where functional redundancy ensures resilience through an insurance effect

First evidence for a massive extinction event affecting bees close to the K-T boundary

Bees and eudicot plants both arose in the mid-late Cretaceous, and their co-evolutionary relationships have often been assumed as an important element in the rise of flowering plants. Given the near-complete dependence of bees on eudicots we would expect that major extinction events affecting the latter would have also impacted bees. However, given the very patchy distribution of bees in the fossil record, identifying any such extinctions using fossils is very problematic. Here we use molecular phylogenetic analyses to show that one bee group, the Xylocopinae, originated in the mid-Cretaceous, coinciding with the early radiation of the eudicots. Lineage through time analyses for this bee subfamily show very early diversification, followed by a long period of seemingly no radiation and then followed by rapid diversification in each of the four constituent tribes. These patterns are consistent with both a long-fuse model of radiation and a massive extinction event close to the K-T boundary. We argue that massive extinction is much more plausible than a long fuse, given the historical biogeography of these bees and the diversity of ecological niches that they occupy. Our results suggest that events near the K-T boundary would have disrupted many plant-bee relationships, with major consequences for the subsequent evolution of eudicots and their pollinators.Sandra M. Rehan, Remko Leys, Michael P. Schwar

The evolution of epigean and stygobitic species of Koonunga Sayce, 1907 (Syncarida: Anaspidacea) in Southern Australia, with the description of three new species

Three new species of Koonunga were discovered in surface and subterranean waters in southern Australia, and were defined using mtDNA analyses and morphology. The new species are: Koonunga hornei Leijs & King; K. tatiaraensis Leijs & King and K. allambiensis Leijs & King. Molecular clock analyses indicate that the divergence times of the species are older than the landscape that they currently inhabit. Different scenarios explaining this apparent discrepancy are discussed in the context of the palaeography of the area. A freshwater epigean origin for Koonunga is considered the most likely hypothesis, whereby some lineages made the transition to the subterranean environment within the last few million years influenced by significant climatic cooling/drying. We discuss the possibility that one stygobitic lineage secondarily regained some of its body pigmentation as adaptation to increased photic conditions after cave collapse and forming of cenotes during the last glacial maximum.Remko Leijs, Tessa Bradford, James G. Mitchell, William F. Humphreys, Steven J. B. Cooper, Peter Goonan, Rachael A. Kin

Conservation of subterranean biodiversity in Western Australia: using molecular genetics to define spatial and temporal relationships

The Jewel Cave karst system in southwestern Australia contains a community of aquatic invertebrates that is listed as critically endangered owing to lowering water levels in cave lakes. A key question for conservation of biodiversity patterns was to determine the most appropriate spatial scale; viz. lake microscale, cave mesoscale, catchment macroscale, or regional megascale). A second key question was to understand the historical relationship between the community and cave water levels, necessary to evaluate the risk of extinction related to predictions of drying climate in southwestern Australia. This study used molecular genetic techniques (allozyme electrophoresis and mitochondrial DNA sequencing) to assess spatial and temporal relationships in two species of crangonyctoid amphipods (Uroctena sp. and Perthia cf. acutitelson Straškraba) from the Jewel Cave system and other karst drainage systems, springs and surface waters in the Leeuwin-Naturaliste karst region. The molecular data indicated the existence of two cryptic species within Perthia cf. acutitelson. Within the Jewel Cave karst system, populations sampled from separate groundwater pools both within and between caves were largely panmictic, with no evidence of population sub-structuring in Uroctena sp. and only a subtle suggestion of heterogeneity in Perthia sp. 1. Beyond the Jewel Cave system, populations of Perthia sp. 1 occurring in separate karst drainage systems and surface catchments are strongly differentiated at the population genetic level. For conservation of biodiversity patterns in Perthia sp. 1 and Uroctena sp., the most appropriate spatial scale is the macrohabitat represented by the karst aquifer or hydrogeologic system. The minimum age estimates, based on molecular clock methods, for divergence of the cave populations from nearby surface populations are 250 ka. The molecular data support the likelihood that the amphipods in Jewel Cave survived in situ lower watertable levels experienced 11 to 13 ka, that coincided with the phase of regional aridity in southwestern Australia near the end of the Pleistocene. However, if the present trend of declining rainfall in southwestern Australia continues, and if water levels in the Jewel Cave system decline below 22.7 m above sea level (ASL), then most of the lakes will become dry and the aquatic invertebrate community will be more vulnerable to extinction because of reduced habitat and consequent reduced population size. -- Authors Open Access - Permission by Publisher See Extended description for more information

A morphological and molecular study of some species in the Camponotus maculatus group (Hymenoptera: Formicidae) in Australia and Africa, with a description of a new Australian species

Abstract Captain Cook is recognised as the collector of Camponotus maculatus (FABRICIUS, 1782) from Sierra Leone and since then many subspecies have been described, most of which are from Africa. One, Camponotus maculatus humilior FOREL, 1902 is common in northern Australia. We describe a morphological and molecular study aimed at determining the relationship of species of the C. maculatus group in Australia and Africa. From this we find no close relationship between the Australian and African species examined. We raise Camponotus maculatus humilior to species rank, synonymise Camponotus villosus CRAWLEY, 1915 with Camponotus novaehollandiae MAYR, 1870 and describe Camponotus crozieri sp.n. We indicate the need for more work in defining the boundaries of Camponotus novaehollandiae