Influences of landscape characteristics and historical barriers on the population genetic structure in the endangered sand-dune subterranean rodent Ctenomys australis

Abstract

Understanding the processes and patterns of local adaptation and migration involves an exhaustive knowledge of how landscape features and population distances shape the genetic variation at the geographical level. Ctenomys australis is an endangered subterranean rodent characterized by having a restricted geographic range immerse in a highly fragmented sand dune landscape in the Southeast of Buenos Aires province, Argentina. We use 13 microsatellite loci in a total of 194 individuals from 13 sampling sites to assess the dispersal patterns and population structure in the complete geographic range of this endemic species. Our analyses show that populations are highly structured with low rates of gene flow among them. Genetic differentiation among sampling sites was consistent with an isolation by distance pattern, however, an important fraction of the population differentiation was explained by natural barriers such as rivers and streams. Although the individuals were sampled at locations distanced from each other, we also use some landscape genetics approaches to evaluate the effects of landscape configuration on the genetic connectivity among populations. These analyses showed that the sand dune habitat availability (the most suitable habitat for the occupation of the species), was one of the main factors that explained the differentiation patterns of the different sampling sites located on both sides of the Quequén Salado River. Finally, habitat availability was directly associated with the width of the sand dune landscape in the Southeast of Buenos Aires province, finding the greatest genetic differentiation among the populations of the Northeast, where this landscape is narrower.

Filling the gap in distribution ranges and conservation status in Ctenomys (Rodentia: Ctenomyidae)

“…Thus, the number of locations is likely to be inflated by considering sampling points as synonyms of collection localities. However, there are cases in which localities have been proven to represent different populations, as occurs in C. australis , which has 13 genetically distinct populations (Austrich et al 2020). The IUCN defines the term location as “a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present” (IUCN 2012).…”

Evaluación de la fragmentación del paisaje en la cuenca de la laguna costera Garzón, Uruguay

“…Trabajos anteriores han demostrado cómo el aumento de actividades antrópicas -incluyendo actividades agrícolas-, el desarrollo urbano y la plantación forestal han provocado la pérdida del hábitat natural y también un incremento de la fragmentación (Rhind, et al, 2001;Kumar, et al, 2018;Austrich, et al, 2020). Consistentemente, este trabajo mostró un aumento en actividades de origen antrópico como cultivos y plantaciones forestales, mientras que áreas naturales como el monte y los herbazales han disminuido su superficie hacia el año 2015.…”

“…Monitoreos continuos sobre la dinámica del paisaje y sus usos, en conjunto con evaluaciones de la calidad de agua del sistema y sus efluentes asociados, se tornan necesarios. Las imágenes satelitales pueden ser una primera fuente de información para este monitoreo de calidad del hábitat incluyendo medidas de conectividad, como lo demuestra este trabajo y otros (Tomaselli, et al, 2012;Austrich, et al, 2020).…”

“…de hábitats naturales ocurren juntos, resultando en una disminución del tamaño de las poblaciones residentes, lo cual aumenta el grado de vulnerabilidad de las especies (Long, et al, 2010). En este sentido, las actividades humanas que promueven la fragmentación del hábitat en sistemas costeros son una de las amenazas más importantes ya que reducen los ecosistemas naturales y afectan el grado de conectividad (Olff y Ritchie, 2002;Austrich, et al, 2020). En este contexto, se vuelven fundamentales los estudios retrospectivos con el propósito de evaluar las causas y consecuencias de las actividades humanas sobre los ecosistemas naturales a largo plazo (Salvati, et al, 2012).…”

Redefining the Distributional Boundaries and Phylogenetic Relationships for Ctenomids From Central Argentina

“…Also, in some coastal and inland areas, C. talarum coexists in close geographic proximity with some species belonging to the mendocinus group ( Ctenomys australis Rusconi, 1934, Ctenomys azarae Thomas, 1903 and Ctenomys porteousi Thomas, 1919; see Contreras and Reig, 1965 ; Carnovale et al, 2017a , b ; Cutrera and Mora, 2017 ; Mapelli et al, 2017 ; Churin et al, 2019 ). Ctenomys talarum is geographically sympatric with C. australis in the southern coastal region of Buenos Aires province ( Contreras and Reig, 1965 ; Malizia et al, 1991 ; Vassallo et al, 1994 ; Vassallo, 1998 ; Busch et al, 2000 ; Justo et al, 2003 ; Mora et al, 2007 ; Cutrera and Mora, 2017 ; Austrich et al, 2020b ), and parapatric with both C. azarae in the east of La Pampa province ( García Esponda et al, 2009 ) and C. porteousi in the southwest of Buenos Aires province near Laguna Epecuén ( Mora et al, 2013 ).…”