Chris H. S. Watts

Evolution of subterranean diving beetles (Coleoptera: Dytiscidae: Hydroporini, Bidessini) in the arid zone of Australia.

Abstract Calcrete aquifers in arid inland Australia have recently been found to contain the worlds most diverse assemblage of subterranean diving beetles (Coleoptera: Dytiscidae). In this study we test whether the adaptive shift hypothesis (ASH) or the climatic relict hypothesis (CRH) is the most likely mode of evolution for the Australian subterranean diving beetles by using a phylogeny based on two sequenced fragments of mitochondrial genes (CO1 and 16S‐tRNA‐ND1) and linearized using a relaxed molecular clock method. Most individual calcrete aquifers contain an assemblage of diving beetle species of distantly related lineages and/or a single pair of sister species that significantly differ in size and morphology. Evolutionary transitions from surface to subterranean life took place in a relatively small time frame between nine and four million years ago. Most of the variation in divergence times of the sympatric sister species is explained by the variation in latitude of the localities, which correlates with the onset of aridity from the north to the south and with an aridity maximum in the Early Pliocene (five mya). We conclude that individual calcrete aquifers were colonized by several distantly related diving beetle lineages. Several lines of evidence from molecular clock analyses support the CRH, indicating that all evolutionary transitions took place during the Late Miocene and Early Pliocene as a result of aridification.

Systematics and evolution of the Australian subterranean hydroporine diving beetles (Dytiscidae), with notes on Carabhydrus

Calcrete aquifers of the Yilgarn area of Western Australia and the Ngalia Basin, Northern Territory, Australia are known to contain a rich invertebrate stygofauna, including the world’s most diverse assemblage of subterranean diving beetles. Here we determine the generic relationships of these subterranean diving beetle species in the tribe Hydroporini and assess their evolutionary origins. Phylogenetic analyses of 1642 base pairs of mitochondrial DNA (mtDNA), comprising segments of CO1, 16S rRNA, tRNAleu and ND1 genes, revealed that the subterranean species from the arid zone, previously classified under the genus Nirripirti Watts & Humphreys (Hydroporini), are all closely related to the genus Paroster Sharp. We synonymise the stygobitic genus Nirripirti with the genus Paroster. Factors that may have been important for the transitions to stygobitic life such as historical and contemporary species distributions, reproductive ecology and body size are discussed. We show that pre-adaptations such as preference for temporary, but seasonally reliable, water and preference to live among gravel and sand along running water would have favoured transitions from surface to stygobitic life, but that large body size may have restricted the likelihood of successful transitions.

Twenty-six New Dytiscidae (Coleoptera) of the Genera Limbodessus Guignot And Nirripirti Watts Humphreys, from Underground Waters in Australia

Summary Twenty-six new species of stygobitic Dytiscidae from inland Western Australia and Central Australia are described: Limbodessus atypicalis, L. barwidgeeensis, L. cooperi, L. exilis, L. leysi, L. gumwellensis, L. harleyi, L. macrohinkleri, L. millbilliensis, L micrommatoion, L. mirandaae, L. melitaensis, L. narryerensis, L. nambiensis, L. palmulaoides, L. phoebeae, L. raeae, L. surreptitius, L. usitatus, L. yandalensis, Nirripirti macrosturtensis, N. megamacrocephalus, N. mesosturtensis, N. microsturtensis, N. septum and N. tetrameres. This brings the total of stygobitic Dytiscidae described from Australia to 80 species in four genera. A key to the known species of Australian stygobitic Dytiscidae is given as well as notes on the physico/chemical properties of selected collecting sites. Geographically the study reinforced our working hypothesis that stygal Dytiscidae in Australia are confined to two discrete areas; the Ngalia Basin northwest of Alice Springs in Central Australia and the Yilgarn Craton in Central Western Australia. As in previous years (see Watts & Humphreys 2004) the stygofauna was found, together with a rich stygobitic fauna largely comprising crustaceans, in those portions of shallow aquifers that ran through areas of calcrete formation. The following new combinations are proposed: Limbodessus bialveus (Watts & Humphreys, 2003), (Tjirtudessus); Limbodessus cunyuensis (Watts & Humphreys, 2003), (Tjirtudessus); Limbodessus hillviewensis (Watts & Humphreys, 2004), (Tjirtudessus); Limbodessus jundeeensis (Watts & Humphreys, 2003), (Tjirtudessus); Limbodessus karalundiensis (Watts & Humphreys, 2003), (Tjirtudessus); Limbodessus macrotarsus (Watts & Humphreys, 2003), (Tjirtudessus); Limbodessus microocular (Watts & Humphreys, 2004), (Tjirtudessus); Limbodessus occidentalis (Watts & Humphreys, 2004), (Boongurrus); Limbodessus padburyensis (Watts & Humphreys, 2004), (Tjirtudessus); Limbodessus silus (Watts & Humphreys, 2003), (Tjirtudessus); Limbodessus sweetwatersensis (Watts & Humphreys, 2003), (Tjirtudessus); Limbodessus wilunaensis (Watts & Humphreys, 2003), (Tjirtudessus); Limbodessus wogarthaensis (Watts & Humphreys, 2004), (Tjirtudessus); and Limbodessus yuinmeryensis (Watts & Humphreys, 2003), (Tjirtudessus). This is the seventh paper in our series describing the stygobitic Dytiscidae of Australia (Watts & Humphreys 1999, 2000, 2001, 2003, 2004; Balke et al. 2004). In it we describe the new species found during fieldwork in Western Australia in the winters of 2003 and 2004.

A highly modified stygobiont diving beetle of the genus Copelatus (Coleoptera, Dytiscidae): taxonomy and cladistic analysis based on mitochondrial DNA sequences

Abstract.  We report the discovery of a new species of Copelatus that is morphologically highly modified for life in groundwater. Copelatus abditus sp.n. was collected from a 4 m deep bore in central Australia. It was placed in Copelatinae based on morphological evidence. This is the first known stygobiont diving beetle that does not belong to the subfamily Hydroporinae. Sequences from the mitochondrial DNA cytochrome oxidase 1, 16S rRNA, tRNAL and NADH dehydrogenase subunit 1 genes suggest that the species belongs to the subgenus Papuadytes, the morphological apomorphies of which are reduced in the new groundwater species. Copelatus (Papuadytes) abditus very much resembles other world stygobiont dytiscids, which all belong to the subfamily Hydroporinae. We suggest that this striking convergence is due to similar selective pressures imposed on all groundwater beetles. We suggest a scenario in which species from temporary habitats evade drought by entering the hyporheic zone, and may be driven to a subterranean existence by desertification of their ancestral habitats, as can be observed in Australia.

Enzyme markers in inbred rat strains: Genetics of new markers and strain profiles

Twenty-six inbred strains of the laboratory rat (Rattus norvegicus) were examined for electrophoretic variation at an estimated 97 genetic loci. In addition to previously documented markers, variation was observed for the enzymes aconitase, aldehyde dehydrogenase, and alkaline phosphatase. The genetic basis of these markers (Acon-1, Ahd-2, and Akp-1) was confirmed. Linkage analysis between 35 pairwise comparisons revealed that the markers Fh-1 and Pep-3 are linked. The strain profiles of the 25 inbred strains at 11 electrophoretic markers are given.

Fourteen New Dytiscidae (Coleoptera) of the Genera Limbodessus Guignot, Paroster Sharp, and Exocelina Broun from Underground Waters in Australia

Abstract Fourteen new species of stygobitic Dytiscidae from inland Western Australia and Central Australia are described: Limbodessus micromelitaensis, L. microbubba, L. lornaensi, L. macrolornaensis, L. yarrabubbaensis, L. trispinosus, L. murrumensis, L. ordinarius, L. nyungduo, L. insolitus, Paroster elongatus, P. novem, P. readi and Exocelina rasjadi. The males of P. tetrameres Watts and Humphreys and P. kurutjutu (Watts & Humphreys) (Kintingka) are described for the first time. This brings the total of stygobitic Dytiscidae described from Australia to 99 species in four genera. One of the new species, Limbodessus insolitus, has single-lobed parameres, the first undoubted member of the tribe Bidessini not to have bilobed parameres. A key to the known species of Australian stygobitic Dytiscidae is given as well as a checklist of the species discovered prior to December 2008. The geographic distribution of this fauna (Fig. 192) and the physico/chemical properties of selected collecting sites (Fig 193, Table 2) and associated fauna (Table 3) are summarised. Geographically, stygal Dytiscidae are now know within Australia from three discrete areas; the Ngalia Basin northwest of Alice Springs in central Australia, the Yilgarn Craton in central Western Australia and the north-east region of New South Wales. In the first two regions the beetles are found in groundwater calcrete formations; in New South Wales the seemingly much sparser fauna is found in coarse alluvial gravels in the upper reaches of rivers. Kintingka Watts & Humphrey is synonymised with Limbodessus Guignot.

Biochemical differentiation among karyotypic forms of Australian Rattus

Isozyme electrophoresis of up to 55 loci, and microcomplement fixation of albumin were used to assess the extent of structural gene divergence among karyotypic forms of Australian Rattus. The results show that the Australian Rattus are monophyletic with respect to R. rattus or R. norvegicus. Within the Australian Rattus, rates of chromosomal evolution have varied enormously, the highest rates being found among members of the R. sordidus group, where extensive chromosomal repatterning has occurred with little or no structural gene divergence.

Larval morphology of four genera of Laccophilinae (Coleoptera: Adephaga: Dytiscidae) with an analysis of their phylogenetic relationships

Descriptions of the larval instars of four genera (12 species) of the dytiscid subfamily Laccophilinae, Laccophilus Leach, Neptosternus Sharp, Australphilus Watts and Africophilus Guignot, are presented including a detailed chaetotaxic and porotaxic analysis of the cephalic capsule, head appendages, legs, last abdominal segment and urogomphi. A parsimony analysis, based on the 13 informative larval characteristics was conducted with Hennig86. The genus Africophilus is postulated to represent the sister-group of a clade comprised of Laccophilus + (Neptosternus + Australphilus) which is supported by, (i) primary seta CO7 articulated proximally on all legs, (ii) presence of natatory setae, (iii) metatibia + metatarsus very elongated, and (iv) elongated urogomphi.

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.

Unveiling the Diversification Dynamics of Australasian Predaceous Diving Beetles in the Cenozoic

During the Cenozoic, Australia experienced major climatic shifts that have had dramatic ecological consequences for the modern biota. Mesic tropical ecosystems were progressively restricted to the coasts and replaced by arid-adapted floral and faunal communities. Whilst the role of aridification has been investigated in a wide range of terrestrial lineages, the response of freshwater clades remains poorly investigated. To gain insights into the diversification processes underlying a freshwater radiation, we studied the evolutionary history of the Australasian predaceous diving beetles of the tribe Hydroporini (147 described species). We used an integrative approach including the latest methods in phylogenetics, divergence time estimation, ancestral character state reconstruction, and likelihood-based methods of diversification rate estimation. Phylogenies and dating analyses were reconstructed with molecular data from seven genes (mitochondrial and nuclear) for 117 species (plus 12 outgroups). Robust and well-resolved phylogenies indicate a late Oligocene origin of Australasian Hydroporini. Biogeographic analyses suggest an origin in the East Coast region of Australia, and a dynamic biogeographic scenario implying dispersal events. The group successfully colonized the tropical coastal regions carved by a rampant desertification, and also colonized groundwater ecosystems in Central Australia. Diversification rate analyses suggest that the ongoing aridification of Australia initiated in the Miocene contributed to a major wave of extinctions since the late Pliocene probably attributable to an increasing aridity, range contractions and seasonally disruptions resulting from Quaternary climatic changes. When comparing subterranean and epigean genera, our results show that contrasting mechanisms drove their diversification and therefore current diversity pattern. The Australasian Hydroporini radiation reflects a combination of processes that promoted both diversification, resulting from new ecological opportunities driven by initial aridification, and a subsequent loss of mesic adapted diversity due to increasing aridity.