Analysis of habitat determinants in contact zones of parapatric European salamanders

Larval development and habitat usage of stream-breeding Fire salamanders in an urban environment

Urbanisation adversely affects the abiotic and biotic characteristics of watercourses, including freshwater streams that support the development of stream-breeding salamanders. We conducted a study over four years on an isolated fire salamander population inhabiting a stream valley northwest of Budapest, Hungary. Our aim was to understand aspects of larval development and habitat usage within this population. The maximum number of larvae was observed in April and the first weeks of May. Due to drifting caused by heavy rainfall, there was a mean decrease of 63.3% in the number of larvae. The abundance of larval salamanders within 16 stream segments showed strong temporal and spatial variation, and there was a strong relationship between larval abundance and the % cover of fine gravel substrate. Some of the larvae could escape drift by entering pools with slower water flow and shelter. Larvae were predominantly solitary in smaller pools but occasionally aggregated in high numbers in some segments. The first larvae with yellow spots (indicative of metamorphosis) appeared in June, and by early September, all larvae were metamorphosing. Our results show that in this urbanised environment, larval development through to metamorphosis is occurring, but increasing urbanisation and alterations to stream flow threaten the persistence of the local population.

Hairstreak butterflies (Lepidoptera, Lycaenidae) and evolution of their male secondary sexual organs

Hairstreak butterflies in the Atlides Section of the Eumaeini are biologically notable for a diverse array of male secondary sexual organs. A "species recognition" hypothesis postulates that females use these organs to choose between conspecific and non-conspecific males, thereby promoting reproductive isolation. Alternately, a "sexual selection" hypothesis posits that females use these organs to choose among conspecific males. These hypotheses need not be mutually exclusive but make different predictions about the evolutionary gain and loss of male secondary sexual organs. We analysed most of the Atlides Section (Theclinae, Eumaeini) phylogenetically. Sister lineages were sympatric at 22 of 37 nodes. Nine evolutionary gains occurred in lineages that were sympatric with their phylogenetic sister, and one occurred in a lineage that was allopatric/parapatric with its sister. By contrast, seven of ten evolutionary losses occurred in lineages that were allopatric/parapatric with their sisters. These results are significantly different from those predicted by a sexual selection hypothesis. We conclude that male secondary sexual organs in the Atlides Section function primarily for species recognition and thereby promote sympatric diversification.

Microhabitat use within a contact zone of parapatric land salamanders in the Swiss Alps

Studies investigating the contact zones in parapatric species can provide valuable insights into the mechanisms that cause range borders. Such studies can also provide a better understanding of the mechanisms which allow coexistence within contact zones. In land salamanders, parapatric range limits among species are often determined by abiotic factors and interspecific competition. The ranges of the parapatric Salamandra salamandra and S. atra narrowly overlap in the European Alps. Climatic gradients that determine their parapatric range margins suggest dissimilar species-habitat-relationships. However, habitat use for these species has not yet been studied in the contact zone where the parapatric ranges overlap and where the species locally co-occur in syntopy. To better understand their parapatric range limits and local syntopy, we compared the species’ microhabitat use in a contact zone in Switzerland and quantified the degree of interspecific niche overlap in relation to resource availability. We observed that most studied microhabitat variables were neither selected nor avoided by the two species, suggesting random use of the habitat for the variables that we studied. Interspecific niche overlap was generally large, but did not differ from that expected by chance. Unlike previous studies that analyzed patterns of co-occurrence of these species at larger spatial scales, we observed no niche differentiation within the contact zone. Both species likely select the same areas that are suitable and available for salamanders while they similarly avoid generally unsuitable habitat. This indicates that niche differentiation can vary depending on the spatial scale where it is investigated.