Co-invasión y spillover de ectoparásitos en la comunidad de roedores nativos e invasores del Santuario de la Naturaleza Península Hualpén, sur de Chile.
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Date
2026
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Universidad de Concepción
Abstract
Las invasiones biológicas son una de las principales razones de cambio en la biodiversidad a nivel global, no sólo por el establecimiento de especies invasoras, sino también por la introducción secundaria de sus parásitos y las alteraciones que pueden generar en las redes parásito-hospedero nativas. En este contexto, pueden ocurrir procesos como la co-invasión, que tiene lugar cuando los parásitos introducidos logran establecerse en hospederos nativos, y el spillover, fenómeno mediante el cual los parásitos se transmiten entre hospederos, ya sea desde invasores hacia nativos o viceversa. Ambos procesos están modulados por factores como el grado de especificidad de los parásitos, la cercanía filogenética entre los hospederos y las condiciones ambientales. El presente estudio evaluó la ocurrencia de co-invasión y spillover de ectoparásitos entre roedores invasores del género Rattus (Rattus rattus y Rattus norvegicus) y roedores nativos (Oligoryzomys longicaudatus y Abrothrix olivacea) en el Santuario de la Naturaleza de la Península de Hualpén (SNPH), un ecosistema ubicado en una zona de transición entre el clima mediterráneo y el clima templado-frío en la Región del Biobío, Chile. Entre los años 2024 y 2025 se realizaron capturas de roedores mediante trampas Sherman y Tomahawk recolectándose ectoparásitos desde los individuos capturados. En total, se capturaron 171 roedores (47 invasores y 124 nativos), a partir de los cuales se recolectaron 5.191 ectoparásitos pertenecientes a cuatro grupos: ácaros, pulgas, garrapatas y piojos. Parte de los ejemplares fueron identificados taxonómicamente mediante caracteres morfológicos y se calcularon parámetros parasitológicos (prevalencia, abundancia media e intensidad media). Además, se estimó el grado de especificidad de los parásitos utilizando el índice de distancia taxonómica promedio (STD) y se evaluó la similitud en la composición de las comunidades de ectoparásitos mediante análisis multivariados (ANOSIM y SIMPER). Se identificaron 21 taxones, correspondientes a 11 ácaros, una especie de garrapata, seis especies de pulgas y tres especies de piojos. De estos, cuatro taxones se registraron exclusivamente en roedores nativos, uno exclusivamente en Rattus spp., y 16 se compartieron entre ambos grupos, evidenciando una dinámica parásito-hospedero compleja con conectividad significativa entre comunidades. Los parámetros parasitológicos mostraron patrones contrastantes entre hospederos, donde Polyplax spinulosa presentó altas prevalencias e intensidades exclusivamente en Rattus spp., mientras que especies como G. wolffsohni presentaron altas prevalencias y abundancias medias sólo en O. longicaudatus. Asimismo, la garrapata Ixodes sigelos presentó altas prevalencias en Rattus spp., lo que sugiere un proceso de spillover desde hospederos nativos a invasores. El STD más bajo se registró en P. spinulosa (STD=1) lo que indica una alta especificidad hacia Rattus spp., mientras que ácaros, pulgas y garrapatas mostraron valores de especificidad intermedios a bajos, lo que sugiere un comportamiento más generalista. Finalmente, el ANOSIM evidenció diferencias significativas en la composición de las comunidades parasitarias entre hospederos nativos e invasores (R=0,1937; p = 0,0001), aunque sí hubo taxones compartidos, lo que indica conectividad entre los hospederos y sus comunidades parasitarias. Se evidenció co-invasión únicamente en Ornithonyssus ca. bacoti, mientras que, en pulgas, garrapatas, piojos y algunas especies de ácaros se observaron eventos de spillover. Este estudio aporta al conocimiento de la dinámica de co-invasión de parásitos en un ecosistema del sur de Chile y destaca la importancia de un monitoreo integral que combine métricas parasitológicas y enfoques ecológicos, con el fin de comprender y predecir los efectos de las invasiones biológicas sobre las comunidades y sus potenciales implicancias sanitarias.
Biological invasions are one of the main drivers of global biodiversity change, not only due to the establishment of invasive species, but also because of the secondary introduction of their parasites and the disruptions this can cause in native parasite-host networks. In this context, processes such as co-invasion, which occur when introduced parasites manage to establish themselves in native hosts, and spillover, a phenomenon whereby parasites are transmitted between hosts, either from invaders to natives or vice versa, can occur. Both processes are modulated by factors such as the degree of parasite specificity, the phylogenetic proximity between hosts, and environmental conditions. The present study evaluated the occurrence of co-invasion and spillover of ectoparasites between invasive rodents of the genus Rattus (Rattus rattus and Rattus norvegicus) and native rodents (Oligoryzomys longicaudatus and Abrothrix olivacea) in the Hualpen Peninsula Nature Sanctuary (SNPH), an ecosystem located in a transition zone between the Mediterranean and temperate-cold climates in the Biobio Region, Chile. Between 2024 and 2025, rodents were captured using Sherman and Tomahawk traps, and ectoparasites were collected from the captured individuals. In total, 171 rodents (47 invasive and 124 native) were captured, from which 5,191 ectoparasites belonging to four groups were collected: mites, fleas, ticks, and lice. Some of the specimens were taxonomically identified based on morphological characteristics, and parasitological parameters (prevalence, mean abundance, and mean intensity) were calculated. In addition, the degree of parasite specificity was estimated using the average taxonomic distance index (STD), and the similarity in the composition of ectoparasite communities was evaluated using multivariate analyses (ANOSIM and SIMPER). Twenty-one taxa were identified, corresponding to 11 mites, one tick species, six flea species, and three louse species. Of these, four taxa were recorded exclusively in native rodents, one exclusively in Rattus spp., and 16 were shared between both groups, indicating complex parasite-host dynamics with significant connectivity between communities. Parasitological parameters showed contrasting patterns among hosts, with Polyplax spinulosa exhibiting high prevalence and intensity exclusively in Rattus spp., while species such as G. wolffsohni exhibited high prevalence and abundance only in O. longicaudatus. Likewise, the tick Ixodes sigelos showed high prevalence in Rattus spp., suggesting a spillover process from native to invasive hosts. The lowest STD was recorded for P. spinulosa (STD=1), indicating high specificity toward Rattus spp., while mites, fleas, and ticks showed intermediate to low specificity values, suggesting a more generalist behavior. Finally, ANOSIM revealed significant differences in the composition of parasitic communities between native and invasive hosts (R = 0.1937; p = 0.0001), although there were shared taxa, indicating connectivity between the hosts and their parasitic communities. Co-invasion was observed only in Ornithonyssus ca. bacoti, whereas spillover events were observed in fleas, ticks, lice, and some mite species. This study contributes to our understanding of the dynamics of parasite co-invasion in an ecosystem in southern Chile and highlights the importance of comprehensive monitoring that combines parasitological metrics and ecological approaches to understand and predict the effects of biological invasions on communities and their potential public health implications.
Biological invasions are one of the main drivers of global biodiversity change, not only due to the establishment of invasive species, but also because of the secondary introduction of their parasites and the disruptions this can cause in native parasite-host networks. In this context, processes such as co-invasion, which occur when introduced parasites manage to establish themselves in native hosts, and spillover, a phenomenon whereby parasites are transmitted between hosts, either from invaders to natives or vice versa, can occur. Both processes are modulated by factors such as the degree of parasite specificity, the phylogenetic proximity between hosts, and environmental conditions. The present study evaluated the occurrence of co-invasion and spillover of ectoparasites between invasive rodents of the genus Rattus (Rattus rattus and Rattus norvegicus) and native rodents (Oligoryzomys longicaudatus and Abrothrix olivacea) in the Hualpen Peninsula Nature Sanctuary (SNPH), an ecosystem located in a transition zone between the Mediterranean and temperate-cold climates in the Biobio Region, Chile. Between 2024 and 2025, rodents were captured using Sherman and Tomahawk traps, and ectoparasites were collected from the captured individuals. In total, 171 rodents (47 invasive and 124 native) were captured, from which 5,191 ectoparasites belonging to four groups were collected: mites, fleas, ticks, and lice. Some of the specimens were taxonomically identified based on morphological characteristics, and parasitological parameters (prevalence, mean abundance, and mean intensity) were calculated. In addition, the degree of parasite specificity was estimated using the average taxonomic distance index (STD), and the similarity in the composition of ectoparasite communities was evaluated using multivariate analyses (ANOSIM and SIMPER). Twenty-one taxa were identified, corresponding to 11 mites, one tick species, six flea species, and three louse species. Of these, four taxa were recorded exclusively in native rodents, one exclusively in Rattus spp., and 16 were shared between both groups, indicating complex parasite-host dynamics with significant connectivity between communities. Parasitological parameters showed contrasting patterns among hosts, with Polyplax spinulosa exhibiting high prevalence and intensity exclusively in Rattus spp., while species such as G. wolffsohni exhibited high prevalence and abundance only in O. longicaudatus. Likewise, the tick Ixodes sigelos showed high prevalence in Rattus spp., suggesting a spillover process from native to invasive hosts. The lowest STD was recorded for P. spinulosa (STD=1), indicating high specificity toward Rattus spp., while mites, fleas, and ticks showed intermediate to low specificity values, suggesting a more generalist behavior. Finally, ANOSIM revealed significant differences in the composition of parasitic communities between native and invasive hosts (R = 0.1937; p = 0.0001), although there were shared taxa, indicating connectivity between the hosts and their parasitic communities. Co-invasion was observed only in Ornithonyssus ca. bacoti, whereas spillover events were observed in fleas, ticks, lice, and some mite species. This study contributes to our understanding of the dynamics of parasite co-invasion in an ecosystem in southern Chile and highlights the importance of comprehensive monitoring that combines parasitological metrics and ecological approaches to understand and predict the effects of biological invasions on communities and their potential public health implications.
Description
Tesis presentada para optar al título de Biólogo/a.
Keywords
Roedores, Parásitos, Organismos introducidos, Biodiversidad