Ecology and conservation of Cephalota (Taenidia) deserticoloides (Codina, 1931) (Coleoptera, Cicindelidae)

Abstract

The use of molecular techniques has become an essential tool to study biological diversity. This is especially important in endangered organisms, where a detailed assessment of their genetic diversity, ecology, and populational status are needed in order to design effective management measures to ensure their survival. Additionally, knowledge of the phylogenetic relationships of organisms is essential for establishing a taxonomic classification coherent with its evolutionary history. Recently, environmental DNA has become an essential source of information about biodiversity that does not require an invasive disturbance of the analyzed taxa. The tiger beetle genus Cephalota, including the subgenera Cephalota and Taenidia, is distributed from the Mediterranean Sea to Central Asia, and includes some endangered endemisms restricted to reduced areas in the Iberian Peninsula. The genesis of this genus has been related to the closure of the Tethys Ocean and the formation of the Mediterranean Sea. Cephalota deserticoloides is an endemic species, with a distribution restricted to a few sites in south eastern Spain, where it occupies only the patchy arid saline steppe type habitat. Due to this high level of patchiness and ecological specialization, its current populations are assumed to be local and isolated. Although regarded as vulnerable, very little is known about its actual population dynamics and degree of endangerment. A capability to assess its presence and identity is paramount to its management, but is confounded by the very similar co-occurrent larvae of C. littorea. The main objective of this thesis is to offer an approach to the knowledge of the evolution of C. deserticoloides, starting with its origin within the Palearctic genus Cephalota, then to focus on the internal dynamics and the relationship between its populations. In the first chapter, a phylogenetic tree of eleven Cephalota species is inferred. The observed phylogenetic relationships between these species challenges the hypotheses previously formulated about the evolution of this group. Additionally, the results do not support the established systematics of this genus, suggesting that the subgenus Taenidia is not monophyletic. The origin of Cephalota is dated back to 13.5 million years ago, once the Mediterranean Sea was already formed. Hypotheses concerning the changes on the suitable habitat for this halophile group caused by fluctuating levels of the Mediterranean Sea are proposed. In the second chapter, we use a twofold approach to assess the population dynamics and origin of C. deserticoloides, combining genetic-based phylogeography with a geometric morphometric approach. The results attest that C. deserticoloides is a small group of isolated populations with little contact with each other. These results improve our understanding of the species and its ecological dynamics, which will enable an improved management and protection of the Iberian saline steppe and of C. deserticoloides. In the third chapter, we use of environmental DNA to conduct a non-invasive sampling of tiger beetle larvae. A novel protocol is developed to discriminate between C. deserticoloides and C. littorea soil-bound genetic material from larval burrows. The observed results confirm the ability of this method to separate both species and give rise to new hypotheses regarding relative abundance and niche partitioning between them. Finally, in the fourth chapter, mark-recapture estimates of total population size are presented for one population of Cephalota deserticoloides. The observations gathered indicate that C. deserticoloides makes a narrow use of the habitat available, with activity peaks that are separated from co-occurrent species. The area under consideration holds a relatively dense tiger beetle population, numerically comparable to those of other endangered cicindelids. These results will help assess the conservation state of C. deserticoloides and set the stage for more long-term efforts to analyse its population viability for protective measures.