The distribution, spatial clustering, and density of trapdoor spiders in two California coastal dune ecosystems

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  The distribution, spatial clustering, and density of trapdoor spiders in two California coastal dune ecosystems Abstract Coastal dune ecosystems support endemic trapdoor spiders, yet population data for these species are limited. We conducted the first coastal dune trapdoor spider population estimation surveys at Moss Landing State Beach (California) and for Aptostichus stephencolberti Bond 2008 at Sunset State Beach using randomly selected 1m 2 quadrats across ~26,000 m 2 per site. Burrow densities were similar between sites (Sunset: 0.287 burrows/m 2 ; Moss: 0.453 burrows/m 2 ), yielding estimated population sizes of ~35,206 and ~30,959 individuals, respectively. However, spatial analyses revealed contrasting patterns of burrow distribution. At Sunset State Beach, burrow presence was strongly associated with vegetation and occurred closer to plants, despite vegetation being randomly distributed. In contrast, no vegetation–burrow association was detected at Moss Landing, alth...

Thinking small: miniaturization might have facilitated adaptation to new niches in tarantulas

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Thinking small: miniaturization might have facilitated adaptation to new niches in tarantulas

Abstract

The interplay between ecology and morphology holds significant importance in the field of evolutionary ecology. Miniaturization, a prevalent trend across diverse branches of the tree of life, often emerges as a consequence of adaptation to specific ecological niches. However, the causes and outcomes of miniaturization can vary significantly among different taxa. In our study, we utilized tarantulas as a model system to explore whether microhabitat choices are linked to morphological characteristics. Specifically, we examined whether the transition to a non-burrowing, ground-dwelling lifestyle is associated with miniaturization. Our findings indicate that the evolution of morphological traits in tarantulas has primarily been influenced by stabilizing selection, with no discernible difference in morphotypes associated with fossorial or arboreal habits. Nevertheless, we observed that whenever tarantulas opportunistically transitioned to a non-burrowing, ground-dwelling lifestyle—such as living under rocks, logs, or within crevices—they seem to have undergone body-form miniaturization and a reduction in the ratio of forelimb to hindlimb length. This study underscores the potential for repeated shifts to unique ecological niches to disrupt the conventional trajectory of morphological evolution, resulting in the emergence of novel phenotypes.

Biswas, A., & Karanth, K. P. Thinking small: Miniaturization might have facilitated adaptation to new niches in tarantulas. Zoological Journal of the Linnean Society. https://doi.org/10.1093/zoolinnean/zlae069