Person:
Santos Martínez, Tomás

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First Name
Tomás
Last Name
Santos Martínez
URI
https://hdl.handle.net/20.500.14352/81651
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Biológicas
Department
Biodiversidad, Ecología y Evolución
Area
Zoología
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2019 - 201912020 - 20231
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Author: Llanos Garrido, Alejandro × Item Type: Publication ×

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    Negative effects of the spatial clumping of thermal resources on lizard thermoregulation in a fragmented habitat
    (Journal of Thermal Biology, 2023) Llanos Garrido, Alejandro; Santos Martínez, Tomás; José A. Díaz
    In ecosystems threatened by the expansion of croplands, habitat fragmentation and climate change, two of the main extinction drivers, may have thermoregulation-mediated interacting effects on demographic trends of terrestrial ectotherms. We studied the thermal biology of a metapopulation of the widespread Mediterranean lacertid Psammodromus algirus in ten fragments of evergreen or deciduous oak forests interspersed among cereal fields. We obtained thermoregulation statistics (selected temperature range, body and operative temperatures, thermal quality of the habitat, and precision, accuracy, and effectiveness of thermoregulation) that could be compared among fragments and with conspecific populations living in unfragmented habitat. We also measured the selection (use vs. availability) and spatial distribution of sunlit and shaded patches used for behavioral thermoregulation in fragments, and we estimated operative temperatures and thermal habitat quality in the agricultural matrix surrounding the fragments. Variation of the thermal environment was much larger within fragments than among them, and thermoregulation was accurate, precise, and efficient throughout the fragmented landscape; its effectiveness was similar to that of previously studied unfragmented populations. The average distance between sunlit and shaded patches was shorter in deciduous than in evergreen fragments, producing a more clumped distribution of the mosaic of thermal resources. Consequently, in evergreen habitat the cost of thermoregulation was higher, because lizards were more selective in their choice of sunlit sites (i.e. they used sunlit patches closer to shade and refuge than expected at random, and the extent of such selection was larger than at deciduous habitat). Temperatures available in croplands were too high to allow lizard dispersal, at least in the post-breeding season. This result confirms the role of croplands as a thermal barrier that promotes inbreeding and associated fitness losses in isolated fragments, and it forecasts a dark future for populations of forest lizards in agricultural landscapes under the combined effects of habitat fragmentation and global warming.
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    Increased individual homozygosity is correlated with low fitness in a fragmented lizard population
    (Biological Journal of the Linnean Society, 2019) Pérez Tris, Javier; Llanos Garrido, Alejandro; Bloor, Paul; Carbonell Alanís, Roberto; Tellería Jorge, José Luis; Santos Martínez, Tomás; Díaz González-Serrano, José Augusto
    Isolation owing to anthropogenic habitat fragmentation is expected to increase the homozygosity of individuals, which might reduce their fitness as a result of inbreeding depression. Using samples from a fragmented population of the lizard Psammodromus algirus, for which we had data about two correlates of fitness, we genotyped individuals for six microsatellite loci that correctly capture genome-wide individual homozygosity of these lizards (as validated with an independent sample of lizards genotyped for both these microsatellites and > 70 000 single nucleotide polymorphisms). Our data revealed genetic structure at a very small geographical scale, which was compatible with restricted gene flow among populations disconnected in a matrix of inhospitable habitat. Lizards from the same fragment were genetically more related to one another than expected by chance, and individual homozygosity was greater in small than in large fragments. Within fragments, individual homozygosity was negatively associated with adult body size and clutch mass, revealing a link among reduced gene flow, increased homozygosity and lowered fitness that might reduce population viability deterministically. Our results contribute to mounting evidence of the impact of the loss of genetic diversity on fragmented wild populations.