Eulamprus

Abstract: Direct interference competition between sympatric taxa affects habitat use and shelter-site selection in species within most major vertebrate lineages. However, studies on interspecific social interference in reptiles largely have been confined to research on interactions between non-native (invasive) species and native fauna. Does interspecific interference also influence habitat use within natural assemblages of reptiles? We studied five broadly sympatric species of viviparous montane skinks within the genera Egernia and Eulamprus in southeastern Australia. Previous work has shown strong interspecific overlap in abiotic attributes of shelter-sites for these taxa, but no joint occupancy of retreats. Laboratory trials in which we manipulated the identity of co-occurring lizards revealed frequent displacement from “preferred” (hotter) shelters, with interspecific interactions more intense than intraspecific conflicts. The five species displayed a linear interspecific dominance hierarchy, with larger species displacing smaller taxa. Field manipulations confirmed that interspecific interactions between these species affect shelter-site use. We conclude that direct agonistic encounters between individuals of different species strongly influence habitat use by lizards within this assemblage.

Abstract: It is relatively easy to document direct agonistic interactions among or within species that lead to exclusion of subordinate animals from preferred habitats. It is more difficult to measure the competitive effects of that exclusion on the ''loser.'' Thus, much behavioral research assumes that the intensity of agonistic interactions is correlated with their cost to performance, but does not directly measure such a cost. We examined fitness- associated traits of pregnant viviparous scincid lizards ( Eulamprus heatwolei) in outdoor enclosures under three conditions: alone, with a conspecific, or with a larger and more aggressive heterospecific (Egernia saxatilis, a sympatric scincid species). As in previous laboratory studies, Egernia saxatilisattacked Eulamprus heatwoleiand excluded individuals of the smaller species from warmer shelter sites. However, Eulamprus heatwoleiwere able to maintain ''normal'' schedules of body temperatures and food intake, apparently by modifying their behavior to minimize encounters with their aggressive cage mates. Ac- cordingly, the subordinate animals showed no overt ill effects in spite of strong agonistic interactions: the body condition, locomotor performance, and corticosterone levels of sub- ordinate Eulamprus housed with Egernia were indistinguishable from those of lizards kept in solitary cages or with conspecifics only. Similarly, the offspring of these pregnant females were born at the same time, and with similar phenotypic traits, as the offspring of control females. Thus, even in situations of intense interspecific aggression and consequent habitat exclusion, behavioral flexibility of the subordinate animals may decrease or eliminate the inferred ecological consequences of that interaction.

Abstract: The water skinks Eulamprus tympanum and Eulamprus heatwolei show thermally induced sex determination where elevated temperatures give rise to male offspring. Paradoxically, Eulamprus species reproduce in temperatures of 12-15 °C making them outliers when compared with reptiles that use temperature as a cue for sex determination. Moreover, these two species are among the very few viviparous reptiles reported to have thermally induced sex determination. Thus, we tested whether these skinks possess undetected sex chromosomes with thermal override. We produced transcriptome and genome data for E. heatwolei. We found that E. heatwolei presents XY chromosomes that include 14 gametologs with regulatory functions. The Y chromosomal region is 79-116 Myr old and shared between water and spotted skinks. Our work provides clear evidence that climate could be useful to predict the type of sex determination systems in reptiles and it also indicates that viviparity is strictly associated with sex chromosomes.

Abstract: Montane (cold-climate) habitats may impose severe thermal constraints on habitat use by ectotherms, favouring strong interspecific convergence in the attributes of suitable shelter-sites. We studied shelter-site use by five species of viviparous scincid lizards in Kanagra Boyd National Park, a montane (1200 m above sea level) forested region 160 km west of Sydney. We scored 21 attributes of 93 shelter-sites (13–20 per species), and the same attributes at unoccupied 'control' sites. These attributes included macrohabitat (e.g. canopy openness, substrate type, distance to waterbodies and logs) as well as shelter-site characteristics (e.g. type of cover-item, size of crevice). Hemispherical-lens photographs and gap-analysis software yielded estimates of solar radiation at each site, and data-loggers recorded temperature profiles in each occupied retreat-site. Principal Components Analysis of the data set identified eight axes of variation. Significant interspecific differences were evident on four of these axes, but with substantial overlap reflecting the broad syntopy of the taxa, plus similarities in characteristics of occupied retreat-sites (e.g. most lizard species utilised sun-exposed shelter-sites with logs nearby). Egernia species (cunninghami, saxatilis, whitii) typically used more open habitats than did Eulamprus (heatwolei, tympanum). Egernia cunninghami used very large crevices, whereas Eulamprus tympanum occupied heavily wooded macrohabitats. At this cold-climate site, interspecific similarities in the characteristics of utilised retreat-sites generated substantial overlap among species in the kinds of sites used, potentially intensifying interference competition among these taxa.