Population structure and genetic variability of mainland and insular populations of the Neotropical water rat, Nectomys squamipes (Rodentia, Sigmodontinae)

Abstract

Seven microsatellite loci were used to investigate the genetic variability and structure of six mainland and two island populations of the Neotropical water rat Nectomys squamipes, a South American semi-aquatic rodent species with a wide distribution. High levels of variability were found within mainland populations while island populations were less variable but the more differentiated in respect to allele number and frequency. The time of biological divergence between mainland and island populations coincided with geological data. A significant geographic structure was found in mainland populations (q = 0.099; r = 0.086) although the degree of differentiation was relatively low in respect to the distance between surveyed localities (24 to 740 km). Genetic and geographic distances were not positively correlated as previously found with random amplified polymorphic DNA (RAPD) markers. Significant but low genetic differentiation in the mainland and lack of isolation by distance can be explained by large population size and/or recent population expansion. Additionally, the agreement between the age of geologic events (sea level fluctuations) and divergence times for insular populations points to a good reference for molecular clock calibration to associate recent environmental changes and the distribution pattern of small mammals in the Brazilian Atlantic Forest.

Peer Review #2 of "Historical connections among river basins and climatic changes explain the biogeographic history of a water rat (v0.1)"

“…When the sea rose to its current level, coastal populations were isolated in the higher areas that became oceanic islands, which is in agreement with the current genetic structure of island populations of N. squamipes (Almeida et al, 2005). Therefore, riparian forests may have functioned as corridors among forest fragments because they have the same resource availability (Naxara, 2008).…”

“…A study on N. squamipes nucleotide variation found a relevant genetic structure , while two others found a shallow structuring among populations of a broader geographical area (Almeida et al, 2000a;. Using randomly amplified polymorphic DNA (RAPD) (Almeida et al, 2000a) and microsatellites (Almeida et al, 2005), these authors PeerJ reviewing PDF | (2018:02:25252:2:0:NEW 20 Jun 2018)…”

Frog size on continental islands of the coast of Rio de Janeiro and the generality of the Island Rule

“…Data regarding anuran species richness by locality used here were presented by Bittencourt-Silva and Silva [ 22 ] and those relating to the bay topography based on nautical charts produced by the Brazilian Navy [ 27 ]. Mainland areas were considered as one locality during the analyses, assuming some degree of connectivity between these populations, as already demonstrated for rodents of the genus Nectomys [ 28 ].…”

Circumpolar genetic population structure of capelin Mallotus villosus

“…Microsatellite data have been less frequently used for estimates of molecular clocks than mtDNA. Almeida et al (2005) presented a formula for estimating divergence time of populations based on microsatellites using the distance δµ 2 , which take into account the SMM. The allele permutation (see above) showed that our data follow IAM, not SMM, and is inappropriate for our data.…”