Stefan M. Eberhard

Cryptic speciation in two widespread subterranean amphipod genera reflects historical drainage patterns in an ancient landscape

The landscape of the Pilbara region of Western Australia has been relatively unchanged for 100 million years. The ancient river systems of this region might be expected to be sources of isolation and divergence for aquatic species. Hence, the occurrence of widespread groundwater taxa in this landscape offers the opportunity to examine associations between genetic diversity and drainage patterns. Pilbarus and Chydaekata are two widespread genera of subterranean amphipods endemic to the Pilbara, each occupying multiple tributaries. We used molecular data to examine the roles of drainage patterns in structuring genetic diversity. Gene flow within a tributary may be facilitated by the occasional occurrence of these amphipods in springs, which results in their downstream dispersal during episodic flooding. However, tributary boundaries may form hydrological barriers to gene flow, resulting in localised isolation of populations and divergence. Samples of both genera, collected throughout three river basins, were examined for sequence divergence in the cytochrome c oxidase I mitochondrial gene. There was no evidence of contemporary gene flow among populations of either genus, and each tributary contained highly divergent lineages, which were not associated with similar morphological differentiation. This suggests cryptic speciation has occurred, and similar phylogenetic signals in both taxa imply similar evolutionary histories. Surface populations may have been driven into subterranean refugia by the cessation of flow in the rivers, associated with Tertiary climate change, while morphological evolution may have been constrained by stabilising selection. The lack of congruence between molecular diversity and morphology raises important practical issues for conservation.

Cryptic Species or Inadequate Taxonomy? Implementation of 2D Geometric Morphometrics Based on Integumental Organs as Landmarks for Delimitation and Description of Copepod Taxa

Discovery of cryptic species using molecular tools has become common in many animal groups but it is rarely accompanied by morphological revision, creating ongoing problems in taxonomy and conservation. In copepods, cryptic species have been discovered in most groups where fast-evolving molecular markers were employed. In this study at Yeelirrie in Western Australia we investigate a subterranean species complex belonging to the harpacticoid genus Schizopera Sars, 1905, using both the barcoding mitochondrial COI gene and landmark-based two-dimensional geometric morphometrics. Integumental organs (sensilla and pores) are used as landmarks for the first time in any crustacean group. Complete congruence between DNA-based species delimitation and relative position of integumental organs in two independent morphological structures suggests the existence of three distinct evolutionary units. We describe two of them as new species, employing a condensed taxonomic format appropriate for cryptic species. We argue that many supposedly cryptic species might not be cryptic if researchers focus on analyzing morphological structures with multivariate tools that explicitly take into account geometry of the phenotype. A perceived supremacy of molecular methods in detecting cryptic species is in our view a consequence of disparity of investment and unexploited recent advancements in morphometrics among taxonomists. Our study shows that morphometric data alone could be used to find diagnostic morphological traits and gives hope to anyone studying small animals with a hard integument or shell, especially opening the door to assessing fossil diversity and rich museum collections. We expect that simultaneous use of molecular tools with geometry-oriented morphometrics may yield faster formal description of species. Decrypted species in this study are a good example for urgency of formal descriptions, as they display short-range endemism in small groundwater calcrete aquifers in a paleochannel, where their conservation may be threatened by proposed mining.

Two new subterranean ameirids (Crustacea : Copepoda : Harpacticoida) expose weaknesses in the conservation of short-range endemics threatened by mining developments in Western Australia

Abstract. The discovery of two new non-marine ameirids from the southern Yilgarn region significantly extends the geographic range for this group in Australia and exposes weaknesses in the conservation and environmental impact assessment (EIA) of subterranean species potentially threatened by mining developments. Megastygonitocrella embe, sp. nov. differs from seven previously described Australian congeners by the armature of the second leg endopod and absence of spinules on the somites. A key to world species of Megastygonitocrella is presented. Phylogenetic analysis based on 57 morphological characters and 30 species belonging to the Stygonitocrella s.l. group suggests that Antistygonitocrella pardalotos, gen. et sp. nov. has no close relatives anywhere in the world. Superficial similarities between the two new species are either plesiomorphies or homoplasies. The habitats of these new short-range endemic species are fractured-rock aquifers developed in Archaean greenstone, where the groundwater is characterised by acid conditions, high salinity and low dissolved oxygen. The population of A. pardalotos is threatened by a mining development. Despite the advanced level of environmental protection policy in Western Australia, our taxonomic study highlights limitations in EIA practices and discusses potential improvements which have global relevance in regions where short-range endemics coincide with extraction of mineral resources.

Groundwater oligochaetes show complex genetic patterns of distribution in the Pilbara region of Western Australia

Abstract. Patterns of genetic diversity in the groundwater fauna of Australia have largely focused on obligate stygobites of relatively large size, namely, crustaceans. Oligochaete worms, with their smaller size and broader ecological niches, provide a contrasting model in which to examine such patterns. Genetic diversity in subterranean oligochaetes in the Pilbara region of Western Australia were examined using one nuclear (18S) and two mitochondrial (COI, 12S) regions. The observed variation was assessed at three levels of hydrology – river basin, creek catchment, and individual bore or site – to document geographic patterns. Most species appeared to be restricted to an individual catchment; however, five species, representing three families, were widespread, with some haplotypes being shared between bores, catchments and even basins. General patterns suggest that while hydrology plays a role in the distribution of oligochaete species, it does not always confine them to catchments, in contrast to patterns observed in groundwater isopods and amphipods in the region. We suggest that intrinsic characteristics of oligochaetes, such as body size, shape, reproductive strategy and ecological requirements, may have allowed them greater dispersal within the subterranean biome of the Pilbara. In particular, oligochaetes may occupy subterranean and surface waters, increasing their opportunities for dispersal.

Austromesocypris bluffensis sp. n. (Crustacea, Ostracoda, Cypridoidea, Scottiinae) from subterranean aquatic habitats in Tasmania, with a key to world species of the subfamily

Abstract Austromesocypris bluffensis sp. n. is described and we report another species, Austromesocypris sp., both collected from subterranean aquatic habitats in Tasmania. This discovery adds a major taxonomic group to the already diverse invertebrate cave fauna of Tasmania, and is of interest because, globally, obligate subterranean aquatic species (stygobites) are poorly represented within the family Cyprididae. The genus Austromesocypris Martens, De Deckker & Rossetti, 2004 is otherwise known to comprise entirely “terrestrial or semi-terrestrial” species. The second species is not described because only juvenile specimens were collected. Both species stand apart from their congeners by the carapace shape, which is rectangular in Austromesocypris bluffensis and triangular and asymmetrical in the unnamed species. Another unique feature of the new species is the almost symmetrical uropodal rami. We also identify some broader systematic issues within the Scottiinae including the position of two New Zealand species, Scottia audax (Chapman, 1961) and Scottia insularis Chapman, 1963 in the genus, and point out their closer relationship to the Gondwana genera of Scottiinae, Austromesocypris and Mesocypris Daday, 1910, than to the Palearctic genus Scottia Brady & Norman, 1889, based on the morphology of the maxillula and mandibula. The identity of the Australian records of Scottia audax (Chapman, 1961), Austromesocypris australiensis (De Deckker, 1983) and the Boreal records of Scottia pseudobrowniana Kempf, 1971 are all considered doubtful. A key to the world species of Scottiinae is provided.