Environmental determinants of the small mammal assemblage in an agroecosystem of central Argentina: The role of Calomys musculinus

Abstract

Agricultural intensification in the central region of Argentina has been accompanied by rodent assemblage changes, involving an increase in Calomys species densities. In particular, Calomys musculinus, the main reservoir of Junín virus (etiological agent of the Argentine Haemorrhagic Fever, AHF) selects field borders over crop-fields. Borders represent relatively-stable habitats within agroecosystems, otherwise highly human modified landscapes. In this article, we assessed the effect of environmental variables on rodent species occurrence and assemblage in the field borders of a pampean agroecosystem. Small rodent occurrence was examined for variation according to vegetation species composition, structure and productivity, using canonical ordination techniques. In a total of 72 crop-field borders of Có rdoba province, in spring, summer and autumn (2005)(2006), we captured 1041 rodents of 8 different species. Akodon azarae, Calomys venustus and C. musculinus were the dominant species of the assemblage, with the first two associated one another, while C. musculinus tended to be related to different environmental variables. We showed that rodent species associations were mediated by resources that changed seasonally, such as vegetation cover. Also, the strength and ''sign'' of the association between species seemed to be a consequence of different habitat preferences and activity patterns. Finally, the intra-annual population cycle seemed to influence the relation between species and habitat structure and, possibly, inter-specific competition for resources. Therefore, we suggest that less generalist species of the rodent assemblage, well adapted to linear habitats, may limit C. musculinus occurrence throughout the agroecosystem by habitat and spatial competition. Any action aimed to control AHF, and therefore C. musculinus population density, should exclude negative effects on coexisting species.

Small mammals in farmlands of Argentina: Responses to organic and conventional farming

“…In this region, the small mammal assemblage is mainly represented by the Cricetidae rodents C. musculinus, C. venustus, C. laucha, A. azarae, A. dolores, Oxymycterus rufus and Oligoryzomys flavescens (Simone et al, 2010). Rodent species were ranked from generalists to specialists considering species-specific habitat specialization; ranging from habitat generalist (species occur in almost all habitats within the agriculture landscape) to habitat specialist (species occur in habitats with high vegetation cover): C. musculinus, C. laucha, A. azarae, O. flavescens, C. venustus, A. dolores and O. rufus (Martínez et al, 2014).…”

“…These linear habitats frequently receive intentional or unintentional spraying of broad-spectrum herbicides from the neighbouring crops (de la Fuente et al, 2010;Ghersa et al, 2002). In intensively managed agricultural landscapes, the maintenance of undisturbed linear habitat networks can attenuate the effects of agricultural intensification by providing suitable habitats for biodiversity conservation (Coda et al, 2014;Gomez et al, 2011;Simone et al, 2010).…”

Environmental variables and reproductive activity in small rodents of pampean agroecosystems

“…This was registered for Calomys musculinus , which was more abundant in active than in inactive borders in summer. The summer season could reflect a particular meaning of habitat quality at the peak of C. musculinus breeding season (de Villafa ñ e and Bonaventura 1987, Mills et al 1991, Mills and Childs 1998, Simone et al 2010. The same response was expected for C. venustus .…”

“…Akodon azarae (Fischer, 1829), Calomys musculinus (Thomas, 1913) and Calomys venustus (Thomas, 1894) are the most abundant species inhabiting the agroecosystems of C ó rdoba Province, mainly present in cropfield edges, roadsides and fencerows habitats (Kravetz and Polop 1983, Polop et al 1985, Andreo et al 2009, Simone et al 2010. These three species show temporal and spatial variations in abundance: they vary seasonally and among habitats of the agroecosystem.…”

“…Calomys musculinus is abundant in field borders but it has been also captured in cropfields (de Villafa ñ e et al 1988, Ellis et al 1997, Busch et al 2000. In a previous study, Simone et al (2010) described rodent-vegetation associations with certain plant species, varying seasonally. This was in agreement with the assumption that the associations with individual plants respond to species-specific requirements at certain time of the year or of the reproductive cycle (Busch et al 2000, Bilenca et al 2007 ).…”