Sympatry and habitat associations of sigmodontine rodents in a neotropical forest-savanna interface

Abstract

Small mammal communities in the Neotropics are composed largely of sigmodontine rodents. However, many questions regarding these communities remain unanswered, especially those pertaining to fine-scale sympatry and habitat selection. To address this, we examined sigmodontine community structure and vegetation in the western margin of the Upper Paraná Atlantic Forest and the southwestern-most extent of the Cerrado (CE) (an extensive South American savanna ecoregion) of Paraguay. Vegetation classifications were derived from satellite imagery combined with maps based on extensive ground-based surveys. The three most abundant species (Akodon montensis, Hylaeamys megacephalus, and Oligoryzomys nigripes) were found most often in microsympatry with conspecifics, and were negatively associated with other species. Akodon montensis was associated with high forest (HF), and H. megacephalus with bamboo understory (BU), whereas O. nigripes did not exhibit a habitat preference. The first two species’ distributions within the landscape were found to be driven primarily by habitat selection, and O. nigripes by a behavioral response (avoidance) to the presence of the other two species. Moreover, habitat influences whether or not a particular species associates with, or avoids, conspecifics or other species.

Mixed Effects of Habitat Degradation and Resources on Hantaviruses in Sympatric Wild Rodent Reservoirs within a Neotropical Forest

“…However, further analysis of station-level vegetation measurements revealed that each grid was heterogeneous ( Figure 4 ; Figure S1 ). As the data suggested that the distribution of these rodents was associated with fine-scale “microhabitat” characteristics ( Table S3 ) [ 36 ], we were interested in whether seropositive mice were also associated with these fine-scale microhabitat types. We therefore employed hierarchical clustering to classify sampling stations into three major clusters according to five of the six vegetation parameters used above to classify degradation level, and each cluster could be defined by specific dominant vegetation characteristics and degradation status ( Figure 4 ; Supplemental Text, Figure S5 ).…”

“…One plausible biological explanation for the dilution effect with respect to hantavirus transmission is that increased species diversity reduces intraspecific contact among reservoir species, potentially due to behavioral changes which arise from interspecific interactions [ 3 , 65 ]. We previously demonstrated that A. montensis , O. nigripes , and the potential spillover species ( H. megacephalus ) have similar habitat preferences [ 34 ] but tend to avoid other species on small spatial scales [ 36 ]. More importantly, fine-scale conspecific associations were detected independently of habitat; thus, the opportunity for intraspecific transmission is similar across all habitats [ 36 ].…”

“…In the neotropical forests of South America, it is clear that the outcome depends primarily on the ecology of rodent–virus interactions within their immediate local environment. We have identified and characterized an ecosystem in a neotropical forest in Paraguay where Akodon montensis and Oligoryzomys nigripes , two sigmodontine rodents, are the primary reservoirs of Jabora and Juquitiba viruses, respectively [ 34 , 35 , 36 , 37 , 38 ]. This system allows us to investigate ecological factors that influence hantavirus prevalence and test whether those factors are species-specific.…”

“…As we have intensively characterized landscape effects on rodent dynamics within this habitat [ 17 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], we could control for landscape- and habitat-specific effects which may otherwise confound studies in the neotropics [ 14 , 16 , 37 , 39 , 43 , 44 ]. This allowed us to control for (and test) the previous observations that habitat degradation may be the primary driver of hantavirus prevalence in neotropical habitats [ 36 , 37 , 40 , 41 , 42 ]. More specifically, we have previously shown that these two rodent reservoir species have fundamentally different microhabitat requirements, defined by vegetation characteristics at a given trap station, yet are sympatric on a marginally larger spatial scale [ 36 , 37 ].…”

“…This allowed us to control for (and test) the previous observations that habitat degradation may be the primary driver of hantavirus prevalence in neotropical habitats [ 36 , 37 , 40 , 41 , 42 ]. More specifically, we have previously shown that these two rodent reservoir species have fundamentally different microhabitat requirements, defined by vegetation characteristics at a given trap station, yet are sympatric on a marginally larger spatial scale [ 36 , 37 ]. This enabled us to test whether these changes in resource augmentation affected fine-scale habitat associations of rodent reservoir abundance and hantavirus prevalence as well as our previously defined larger scale associations of habitat degradation [ 17 , 40 ].…”