We published a comprehensive phylogeny of a model spider group, the family Nephilidae, known for female and web gigantism and for extreme sexual size dimorphism with males over 100 times lighter than the females. These spiders are therefore model organisms for many biological studies, but prior phylogenies have been deficient and incomplete. Our paper adds a new phylogeny, based on modern phylogenetic analyses using 367 genetic markers and a new fossil time calibration. The work provides the foundation for understanding nephilid evolutionary history. Specifically, it finds no support for biological rules, such as Rensch's and Cope's Rules, as well as for sexually correlated size evolution. The phylogeny of Nephilidae, a group renowned for extreme phenotypes and silk properties, provides the foundation for understanding its evolutionary history. This work contributes to understanding of phenotypic evolution emphasizing body size. This work is the basis for our further studies, from the evolution of webs and silk properties, to sexual selection, behavioural biology, evolutionary ecology, and the evolution of sexual dimorphism.
COBISS.SI-ID: 44009773
Sexual size dimorphism (SSD) is one of the most striking animal traits. While male-biased SSD is common (particularly in vertebrat es) and is readily explained by sexual selection for larger males, female-biased SSD is not confined to particular clades but is evidently a more complicated outcome of gendered evolutionary drivers whose strength and direction are diverse. Extreme SSD (eSSD), which is defined as females twice or more the male size, has been identified in 16 spider clades. We propose drivers of SSD in spiders within the differential equilibrium model and defined the eSSD mating syndrome. We hypothesized that in the long run, the costs of female gigantism might become very high, and result in an evolutionary dead end. We proposed the differential equilibrium model which, explains SSD evolution as the sum of several, possibly opposing, selective forces on each sex, however pathways and pressures are clade, species, and context specific. This article reviews our past behavioural studies, and identifies high correlation between eSSD and extreme sexual strategies, termed the eSSD mating syndrome This review is a basis for our further studies on processes that can modify biotic diversity on multiple levels.
COBISS.SI-ID: 5289551
n the karst landscape of Kras Plateau (SW Slovenia), we studied the impact of historic human-induced land degradation on biodiversity by studying the characteristics and changes in vegetation of degraded and non-degraded karst depressions (dolines). Intensive human-induced land degradation began as a consequence of the abandonment of traditional land use, thus many dolines have disappeared by being completely filled with waste material and overgrown. The study is based on a chronosequence approach and assesses whether vegetation (e.g. community succession stages) can be used as an (bio)indicator of land degradation to estimate approximately the duration of degradation on the basis of the stage of succession. Ecological evaluation was based on sampling the floristic composition and the topsoil. In this study, three vegetation measures were established as indicative of degradation: (1) the appearance of ruderal species, (2) hemeroby and (3) alien and invasive species. A succession model of degraded karst landscape was produced based on identified chronosequences to assess the long-term spatial impact of doline degradation on karst biodiversity. The model is showing the tendency towards the vegetation homogenization of karst landscape. The research deals with process of changes of soils and vegetation in time. We found out the potential (bioi)indicators for monitoring of succession (changes in vegetation and landscape) and established the tendency of vegetation in the karst landscape.
COBISS.SI-ID: 43363629
Current climate change has led to latitudinal and altitudinal range expansions of numerous species. During such range expansions, plant species are expected to experience changes in interactions with other organisms, especially with belowground biota that have a limited dispersal capacity. Nematodes form a key component of the belowground food web as they include bacterivores, fungivores, omnivores and root herbivores. Their community composition under climate change-driven intracontinental range-expanding plants has been studied almost exclusively under controlled conditions, whereas little is known about actual patterns in the field. We use novel molecular sequencing techniques combined with morphological quantification in order to examine nematode communities in the rhizospheres of four range-expanding and four congeneric native species along a 2,000 km latitudinal transect from South-Eastern to North-Western Europe. We tested the hypotheses that latitudinal shifts in nematode community composition are stronger in range-expanding plant species than in congeneric natives and that in their new range, range-expanding plant species accumulate fewest root-feeding nematodes. We conclude that variation in nematode community composition with increasing latitude occurs for both range-expanding and native plant species and that some range-expanding plant species may become released from root-feeding nematodes in the new range. The research contributes to a better understanding of changing global patterns of biodiversity of plant communities and the processes that shape them. It indicates ways of shaping life strategies of expansive species and the reasons for their greater success in responding to environmental changes due to anthropogenic pressures. The study can be the basis for further research and more accurate predictions of the impact of climate change on biogeographic patterns of flora and vegetation and on the biogeographic dynamics of alien species.
COBISS.SI-ID: 44826413
Vicariance and dispersal events, combined with intricate global climatic history, have left an imprint on the spatiotemporal distribution and diversity of many organisms. Anelosimus spiders (Theridiidae), range from solitary to social, with a cosmopolitan distribution in temperate- to-tropical areas. Their evolutionary history and the discontinuous distribution of species richness suggest that 1) long distance overwater dispersal, and 2) climate change during the Neogene (23–2.6?Ma), may be major factors in explaining their distribution and diversification. Here we tested these hypotheses, by investigating the phylogeny and spatiotemporal biogeography of Anelosimus through a culmination of a 20-year comprehensive global sampling at the species level. Our results strongly support the monophyly of Anelosimus with an Oligocene (~30?Ma) South American origin. Major clades on other continents originate via multiple, long-distance dispersal events, of solitary or subsocial—but not social—lineages, from the Americas. The early diversification of Anelosimus spiders coincides with a sudden thermal increase in the late Oligocene (~27–25?Ma), though no causal connection can be made. Our results, however, strongly support the hypothesis that global Neogene climatic cooling in the last 8?Ma drove Anelosimus radiation in parallel in S. America and Madagascar, offering a rare empirical evidence for diversification of a socially diverse group driven by an interplay between long distance dispersal and global Neogene climatic changes. Understanding of how past climatic and ecological patterns correlate with diversification history could help predict response to future major climatic events, such as ongoing unprecedented rates in global climate and habitat changes. For example, given that only subsocial and solitary species of Anelosimus have made intercontinental shifts, while social species have not, and this reflects intrinsic biological abilities that relate to aerial dispersal, it may be foreseen that the ongoing global changes in climate and habitat availability will affect the social lineages more than the more mobile subsocial and solitary ones.
COBISS.SI-ID: 13831939