Name: Silva TL

Biodeserts supervisor: Brito JC

Co-supervisors: Alves PC, Teresa Abáigar, Estación Experimental de Zonas Áridas, EEZA-CSIC, Spain

Title: Biodiversity, evolution and conservation of threatened desert ungulates

Institution: University of Porto

Status: Completed



Biodiversity is declining at a global level as a consequence of habitat loss and climate change. Human exploitation activities in deserts and arid regions are increasing, and the progressive aridity conditions experienced in these regions are negatively affecting local biodiversity distribution patterns. Most of North Africa is occupied by the Sahara-Sahel ecoregions that comprise the world’s largest warm desert and the neighbouring arid regions to the south. Multiple Sahara-Sahel species are listed as threatened by the IUCN Red List of Threatened Species. In this region, ungulates are represented by five gazelles, Eudorcas rufifrons, Gazella cuvieri, G. dorcas, G. leptoceros, and Nanger dama, and three large-sized ungulates: Addax nasomaculatus, Ammotragus lervia, and Oryx dammah. Two threatened gazelles, G. bennettii and G. subgutturosa, are present in the Central Arid Plateaux of Iran. The megafauna is one of the most threatened groups of animals on Earth, experiencing strong declines in population size and range. The main cause for the decline of desert ungulates throughout their ranges is illegal hunting, but changes in land-cover/land-use, climate change, and increasing natural resources extraction, agricultural encroachment and competition from livestock are also reasons for the decline.
The general aim of this thesis was to contribute for the conservation planning of threatened ungulates, particularly of North African gazelles. This aim was achieved by delineating four main objectives: i) increasing the available molecular methods for genetic identification of endangered North African ungulates without the need of invasive sampling; ii) clarifying the phylogenetic relationships between threatened North African gazelles and identifying potential occurrence areas; iii) understanding relationships between the genetic diversities of 12 African ungulates and their observed range regression patterns and intrinsic and extrinsic factors; and iv) evaluating the genetic structure of an Asian gazelle and the effects of landscape features on gene flow patterns.
The main results found were:
1. Noninvasive sampling provides a useful approach to obtain ecological and genetic information essential to guide conservation actions. The very first step in conservation planning is to accurately identify species. We developed a simple, high reliable and low cost molecular method based on polymorphisms in small fragments of the mitochondrial cytochrome b and the nuclear kappa casein gene for identifying endangered North African ungulates. These fragments revealed polymorphisms, including species-specific variation, which allowed species identification of nine ungulate species that co-occur in North Africa. The method was validated across more than 1000 samples, including different types of noninvasive samples collected in the field.
2. Conservation planning of threatened taxa relies upon accurate data on systematics, ecological traits and suitable habitats. Within the genus Gazella, taxonomy and systematics are not very clear so far. Despite the research efforts done in the last few years, there are still several uncertainties. Using molecular and ecological tools, we clarified phylogenetic relationships in the genus Gazella, and identified ecotypes and evolutionary significant units. Gazella cuvieri and G. leptoceros loderi comprise a single monophyletic group; the populations of these taxa occupy distinct geographic areas and specific environments, and they correspond to mountain and lowland ecotypes of G. cuvieri, respectively.
3. The genetic diversity of 12 African ungulates are the lowest in the species that have suffered the largest range regressions and were mostly related with environmental variation and human pressure variables. The measured realized ecological niche overlap of historical and present distributions of 12 African ungulates based in environmental variables and human pressure variables was low or completely non-overlapping, indicating strong niche shifts along time. Extant populations are likely occupying the last strongholds of suitable habitats, which are retaining the highest observed genetic diversities among all taxa. Extant populations occur under harsher environmental conditions, and thus may be vulnerable to the frequent drought periods that characterise North Africa.
4. Gazella subgutturosa in the Central Arid Plateaux of Iran comprises three genetically homogeneous populations and there is restricted dispersal between populations. Geographic distances were found to be related with genetic distance and there were low effects of anthropogenic barriers on observed genetic structure. A combination of geographic distance, landscape resistance, and anthropogenic factors are affecting the genetic structure and gene flow of gazelle populations. Future road construction might impede connectivity and gene exchange of populations.
Evidence of promising tools to improve knowledge on the biology of North African ungulates and consequently, the implementation of more efficient management and conservation plans for these threatened ungulates, are provided in this thesis. In the future, conservation planning of ungulates should consider the preservation of
ecotypes to help maintaining the overall adaptive potential of the species. Conservation measures should consider also some isolated population as separate management units.