Leticia Bidegaray-Batista

Living on the edge: demographic and phylogeographical patterns in the woodlouse-hunter spider Dysdera lancerotensis Simon, 1907 on the eastern volcanic ridge of the Canary Islands

The Eastern Canary Islands are the emerged tips of a continuous volcanic ridge running parallel to the northeastern African coast, originated by episodic volcanic eruptions that can be traced back to the Miocene and that, following a major period of quiescence and erosion, continued from the Pliocene to the present day. The islands have been periodically connected by eustatic sea‐level changes resulting from Pleistocene glacial cycles. The ground‐dwelling spider Dysdera lancerotensis Simon, 1907 occurs along the entire ridge, except on recent barren lavas and sand dunes, and is therefore an ideal model for studying the effect of episodic geological processes on terrestrial organisms. Nested clade and population genetic analyses using 39 haplotypes from 605 base pairs of mitochondrial DNA cytochrome c oxidase I sequence data, along with phylogenetic analyses including two additional mitochondrial genes, uncover complex phylogeographical and demographic patterns. Our results indicate that D. lancerotensis colonized the ridge from north to south, in contrast to what had been expected given the SSW‐NNE trend of volcanism and to what had been reported for other terrestrial arthropods. The occurrence of several episodes of extinction, recolonization and expansion are hypothesized for this species, and areas that act as refugia during volcanic cycles are identified. Relaxed molecular clock methods reveal divergence times between main haplotype lineages that suggest an older origin of the northern islets than anticipated based on geological evidence. This study supports the key role of volcanism in shaping the distribution of terrestrial organisms on oceanic islands and generates phylogeographical predictions that warrant further research into other terrestrial endemisms of this fascinating region.

The Imprint of Geologic History on Within-Island Diversification of Woodlouse-Hunter Spiders (Araneae, Dysderidae) in the Canary Islands

Geological processes and ecological adaptation are major drivers of diversification on oceanic islands. Although diversification in these islands is often interpreted as resulting from dispersal or island hopping rather than vicariance, this may not be the case in islands with complex geological histories. The island of Tenerife, in the Canary Islands, emerged in the late Miocene as 3 precursor islands that were subsequently connected and reisolated by volcanic cycles. The spider Dysdera verneaui is endemic to the island of Tenerife, where it is widely distributed throughout most island habitats, providing an excellent model to investigate the role of physical barriers and ecological adaptation in shaping within-island diversity. Here, we present evidence that the phylogeographic patterns of this species trace back to the independent emergence of the protoislands. Molecular markers (mitochondrial genes cox1, 16S, and nad1 and the nuclear genes ITS-2 and 28S) analyzed from 100 specimens (including a thorough sampling of D. verneaui populations and additional outgroups) identify 2 distinct evolutionary lineages that correspond to 2 precursor islands, each with diagnostic genital characters indicative of separate species status. Episodic introgression events between these 2 main evolutionary lineages explain the observed incongruence between mitochondrial and nuclear markers, probably as a result of the homogenization of their ITS-2 sequence types. The most widespread lineage exhibits a complex population structure, which is compatible with either secondary contact, following connection of deeply divergent lineages, or alternatively, a back colonization from 1 precursor island to another.

Imprints of multiple glacial refugia in the Pyrenees revealed by phylogeography and palaeodistribution modelling of an endemic spider

Mediterranean mountain ranges harbour highly endemic biota in islandlike habitats. Their topographic diversity offered the opportunity for mountain species to persist in refugial areas during episodes of major climatic change. We investigate the role of Quaternary climatic oscillations in shaping the demographic history and distribution ranges in the spider Harpactocrates ravastellus, endemic to the Pyrenees. Gene trees and multispecies coalescent analyses on mitochondrial and nuclear DNA sequences unveiled two distinct lineages with a hybrid zone around the northwestern area of the Catalan Pyrenees. The lineages were further supported by morphological differences. Climatic niche‐based species distribution models (SDMs) identified two lowland refugia at the western and eastern extremes of the mountain range, which would suggest secondary contact following postglacial expansion of populations from both refugia. Neutrality test and approximate Bayesian computation (ABC) analyses indicated that several local populations underwent severe bottlenecks followed by population expansions, which in combination with the deep population differentiation provided evidence for population survival during glacial periods in microrefugia across the mountain range, in addition to the main Atlantic and Mediterranean (western and eastern) refugia. This study sheds light on the complexities of Quaternary climatic oscillations in building up genetic diversity and local endemicity in the southern Europe mountain ranges.

Winter is coming: Miocene and Quaternary climatic shifts shaped the diversification of Western‐Mediterranean Harpactocrates (Araneae, Dysderidae) spiders

Past climatic shifts have played a major role in generating and shaping biodiversity. Quaternary glacial cycles are the better known examples of dramatic climatic changes endured by ecosystems in temperate regions. Although still a matter of debate, some authors suggest that glaciations promoted speciation. Here we investigate the effect of past climatic changes on the diversification of the ground‐dwelling spider genus Harpactocrates, distributed across the major mountain ranges of the western Mediterranean. Concatenated and species‐tree analyses of multiple mitochondrial and nuclear loci, combined with the use of fossil and biogeographic calibration points, reveal a Miocene origin of most nominal species, but also unravel several cryptic lineages tracing back to the Pleistocene. We hypothesize that the Miocene Climatic Transition triggered major extinction events in the genus but also promoted its subsequent diversification. Under this scenario, the Iberian mountains acted as an island‐like system, providing shelter to Harpactocrates lineages during the climate shifts and favouring isolation between mountain ranges. Quaternary glacial cycles contributed further to the diversification of the group by isolating lineages in peripheral refugia within mountain ranges. In addition, we recovered some unique biogeographic patterns, such as the colonization of the Alps and the Apennines from the Iberian Peninsula.

Bringing spiders to the multilocus era: novel anonymous nuclear markers for Harpactocrates ground-dwelling spiders (Araneae: Dysderidae) with application to related genera

Abstract Multilocus approaches are essential for accurately recovering the evolutionary processes underlying species and population history. However, historical inferences in non-model organisms are still almost exclusively based on mitochondrial DNA due to the difficulty of obtaining multiple informative loci. Here, we use a genomic library based approach, to generate 15 novel anonymous nuclear markers (ANMs) from the ground spider Harpactocrates globifer Ferrández 1986. The ANMs cross-amplify and sequence well in the target species and its two closest relatives, and some of them also in the more distantly related H. ravastellus Simon 1914. Levels of nucleotide diversity of the ANMs within H. globifer ranged from 0.05% to 1.4% and average sequence divergence between close congeneric relatives from 0.02% to 13.9%, supporting the utility of these loci in population and species-level analyses. Moreover, a cross-species amplification screened in other spider taxa showed that some of the loci could also potentially be useful in more distantly related genera.

Endemism and evolution in the littoral woodlouse Halophiloscia Verhoeff, 1908 (Crustacea, Isopoda, Oniscidea) from the Canary Islands: implications for conservation policies

The woodlouse genus Halophiloscia Verhoeff, 1908 includes littoral halophilous species distributed along the coasts of the Mediterranean Sea, the Atlantic coasts of Europe and northern Africa. The species Halophiloscia couchii has been introduced to the Americas, Hawaii and Australia. The Canary Islands harbour four species, two of which are included in catalogues of endangered species. One mitochondrial and one nuclear gene sequenced from over 100 specimens, including outgroups, were analysed to infer the colonisation and diversification processes of Halophiloscia in the Canary Islands and shed light on their conservation status. The Canary Islands were independently colonised by three distinct Halophiloscia lineages: (i) the endemic species H. rodriguezi, collected in several western Canary Islands, and the troglobiomorphic H. microphthalma from La Palma, (ii) the endemic H. canariensis, found throughout the eastern Canaries, and (iii) the cosmopolitan H. couchii, present on Gran Canaria and Tenerife. Halophiloscia microphthalma is not sister to the extant epigean Halophiloscia species present on the same island, which together with the low levels of genetic variability detected in the species may warrant a higher conservation status than presently given. The mitochondrial marker revealed a fine‐scale phylogeographic structure in H. canariensis, and rejected recent sharp declines in its population size, which in addition to its widespread distribution challenge its consideration as an endangered species. The presence of H. couchii in the archipelago is interpreted as a recent introduction. Although no evidence of introgression was detected, more thorough sampling and monitoring of introduced populations are recommended to discard either hybridisation or competitive displacement of native species.

Flying sand-dwelling spiders: aerial dispersal in Allocosa marindia and Allocosa senex (Araneae: Lycosidae)

Abstract Aerial dispersal in spiders or ballooning is typically considered to occur during the day by juvenile instars or small-sized adults. Allocosa marindia Simó, Lise, Pompozzi & Laborda, 2017 and Allocosa senex (Mello-Leitão, 1945) are two nocturnal wolf spiders that inhabit coastal sandy beaches of South America. As mothers of both species emerge from the burrows during the night to disperse the spiderlings, we expected that aerial dispersal of spiderlings could occur during that period. Our aim was to test ballooning occurrence in both species during day and night under laboratory conditions, using as a positive control, the wolf spider Schizocosa malitiosa (Tullgren, 1905). We examined ballooning behavior of once-molted spiderlings of A. marindia, A. senex and S. malitiosa, under diurnal and nocturnal conditions, recording observations in a container with grasses and sand as substrate. We exposed the spiderlings to air flow and recorded occurrences of climbing the grass, dropping on dragline and tip-toeing (pre-ballooning behaviors). The three species performed pre-ballooning behaviors during the day but also in the night, and the occurrences of these behaviors varied both within and among species. More events of pre-ballooning behavior were observed during the day than during the night. However, we found differences in the number of events of tip-toeing and dropping on dragline according to the time of the day. We discuss the possibility that microhabitat conditions could affect ballooning propensity particularly in the three coastal wolf spiders.

Dispersal Strategies, Genetic Diversity, and Distribution of Two Wolf Spiders (Araneae, Lycosidae): Potential Bio-Indicators of Ecosystem Health of Coastal Dune Habitats of South America

Dispersal strategies are essential for species survival. Animals need to move to search for food, to locate potential sexual partners, to find refuge and escape from predators, and to avoid inbreeding and local competition for resources. The degree of plasticity of those traits will determine the ability of the species or population to respond successfully to changes in the environment, which is particularly important in species with a restricted habitat. Allocosa marindia and Allocosa senex are two nocturnal lycosids that construct burrows along the sandy coasts of Argentina, Brazil, and Uruguay. Both species show a reversal in the typical sex roles and size dimorphism expected in spiders: females are the mobile and courting sex, and males are larger than females. A. marindia and A. senex are strictly associated to coastal sand dunes with scarce native vegetation. During recent decades, the South American coastline has been reduced and disturbed due to urbanism and touristic activities, leading to the isolation of populations of Allocosa species. In the present chapter, we review the available information about the natural history of Allocosa species, providing data about their mechanisms of dispersal, distribution, genetic diversity, and spatial patterns of genetic variation, as well as their role as biological indicators for the coastlines of Southern South America. We integrate information provided by dispersal behavior data, genetic data, and GIS (geographic information systems) and SDMs (species distribution models) tools, and discuss the predictive maps of distribution for each species and their possible fate under a global-warming scenario.