Genetic diversity and differentiation in the leaf litter weevil Geochus politus across an urban-rural gradient

Abstract

Urban reserves have the potential to retain relatively high biodiversity. However, populations of the taxa within them can have reduced genetic diversity and, if gene flow between populations is inhibited by urbanised surroundings, can become genetically differentiated. Here we determine whether differences in population genetic differentiation and diversity can be observed in the leaf litter inhabiting weevil Geochus politus along the urban-rural gradient spanning Waitākere Ranges Regional Parkland and suburbs of West Auckland, New Zealand. Nine microsatellite markers were developed and screened across 300 individuals from nine sampling locations. Pairwise F ST values, a principal coordinates analysis, and Bayesian estimates of population structure all demonstrated that the most urban site was strongly differentiated from the others. This site also had the lowest heterozygosity and highest F IS values, potentially indicating a loss of genetic variation and a greater degree of inbreeding, although not to a dramatic extent. Differentiation was also observed among sampling locations within continuous forest, suggesting that both urbanisation and other landscape variables are influencing gene flow between these locations. This study highlights the potential for urban reserves to harbour significant diversity and emphasises the importance of maintaining these sites.

Genetic diversity and gene flow of the soil arthropod (Scolopendra mutilans) in urban landscapes: The roles of rivers, mountains and fragmentation

“…For most animals, habitat fragmentation does hinder gene flow between populations (Blanchong et al, 2013; Brav‐Cubitt et al, 2022; Chen et al, 2022). However, gene flows in bog fritillary butterfly and black widow spider populations were unaffected and even increased in urban settings (Miles et al, 2018; Neve et al, 2008).…”

Cuando los insectos no vuelan, ¿las vialidades y la infraestructura urbana actúan siempre como barreras?

“…A pesar de los ejemplos anteriores, realizamos una búsqueda exhaustiva en la literatura sobre insectos no voladores rurales y urbanos que han podido mantener su conectividad, a pesar de la existencia de vialidades y asentamientos humanos. Para nuestra sorpresa, encontramos la existencia de siete especies de insectos cursores, cuyas poblaciones están conectadas pese a la presencia de vialidades e infraestructura urbana: el escarabajo Bembidion lampros en Kallø y Bjerringbro, Dinamarca (Marchi et al, 2013), la hormiga armada o marabunta, Eciton burchellii, en el bosque de San Lorenzo, Panamá (Pérez-Espona et al, 2012), el escarabajo Geochus politus en Auckland, Nueva Zelanda (Brav-Cubitt et al, 2022), los saltamontes Stethophyma grossum y Gomphocerippus rufus en Oberaagau, Suiza (Keller et al, 2013a;2013b), la esperanza Metrioptera bicolor en Hassberge, Alemania (Heidinger et al, 2013) y el grillo de la madera, Nemobius sylvestris, en la isla de Wight en Inglaterra (Watts et al, 2016). Pero, ¿cómo es que estos insectos mantienen la conexión entre sus poblaciones?…”

“…Pero, ¿cómo es que estos insectos mantienen la conexión entre sus poblaciones? El escarabajo Geochus politus cruza las vialidades durante periodos de inundación (Brav-Cubitt et al, 2022) para evitar las altas temperaturas que alcanza el concreto en época de secas; mientras que Bembidion lampros, otro escarabajo, utiliza los setos cubiertos por árboles (Marchi et al, 2013) para evitar la insolación.…”