Ontogenetic and geographic venom variation in the Great Basin Rattlesnake, Crotalus oreganus lutosus

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  Ontogenetic and geographic venom variation in the Great Basin Rattlesnake, Crotalus oreganus lutosus Abstract Venom composition among the species of the Western Rattlesnake clade is often quite variable, depending on several factors such as geographic location and ontogeny. Venom composition not only affects the ability of a snake to acquire prey efficiently, but it can also significantly impact snakebite symptomology. Currently, there has been limited characterization of the venom from the Great Basin Rattlesnake ( Crotalus oreganus lutosus ), a lineage that is broadly distributed in the intermontane western United States. In this study we sample 67 individual Great Basin Rattlesnakes collected in Idaho, Utah, California, and Arizona. We find evidence for substantial ontogenetic and geographic variation in venom composition. Of the six toxin families assessed, all showed ontogenetic shifts to varying extents, with some trends differing from those observed in other rattlesnake sp...

Urban Spider Assemblages in a Neotropical City: Diversity, Functional Composition, and Introduced Species in Public Parks of Chetumal, Mexico

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Urban Spider Assemblages in a Neotropical City: Diversity, Functional Composition, and Introduced Species in Public Parks of Chetumal, Mexico

Abstract

Urban parks in rapidly expanding tropical cities function as novel ecosystems where habitat filtering, human-mediated dispersal, and management practices can shape arthropod assemblages. Spiders are useful indicators of these processes because they combine high taxonomic diversity, functional heterogeneity, and sensitivity to microhabitat structure. Here, we evaluated whether public urban parks in Chetumal, Mexico, sustain diverse spider assemblages while also showing signals of urban biotic mixing, functional filtering, and detectability biases in citizen-science records. We sampled 20 parks using two daytime techniques, look-up and look-down searching, and compared the results with citizen science observations. In total, we collected 4870 spiders belonging to 27 families, 100 genera, and 167 species. The richest families were Salticidae, Araneidae, and Theridiidae, whereas abundance was mainly driven by Tetragnathidae, Lycosidae, and Oecobiidae, indicating a highly uneven community structure. Inventory completeness was high according to rarefaction and coverage analyses. Nine introduced species were detected, representing about 18% of all individuals, which suggests urban mixing. Only one medically important species, Loxosceles yucatana, was recorded, and it was rare. Spider communities included all major hunting guild strategies, especially orb-web weavers and ground hunters, highlighting the ecological value of urban parks as biodiversity reservoirs in a rapidly urbanizing Neotropical region.

Noh Gomez JM, Lucio-Palacio CR, Machkour-M’Rabet S, Legal L, Henaut Y. Urban Spider Assemblages in a Neotropical City: Diversity, Functional Composition, and Introduced Species in Public Parks of Chetumal, Mexico. Diversity. 2026; 18(6):327. https://doi.org/10.3390/d18060327