The Amazon River system as an ecological barrier driving genetic differentiation of the pink dolphin (Inia geoffrensis)

Abstract

The pink dolphin (Inia geoffrensis) is widely distributed along the Amazon and Orinoco basins, covering an area of approximately 7 million km 2 . Previous morphological and genetic studies have proposed the existence of at least two evolutionary significant units: one distributed across the Orinoco and Amazon basins and another confined to the Bolivian Amazon. The presence of barriers in the riverine environment has been suggested to play a significant role in shaping present-day patterns of ecological and genetic structure for this species. In the present study, we examined the phylogeographic structure, lineage divergence time and historical demography using mitochondrial (mt)DNA sequences in different pink dolphin populations distributed in large and small spatial scales, including two neighbouring Brazilian Amazon populations. mtDNA control region (CR) analysis revealed that the Brazilian haplotypes occupy an intermediate position compared to three previously studied geographic locations: the Colombian Amazon, the Colombian Orinoco, and the Bolivian Amazon. On a local scale, we have identified a pattern of maternal isolation between two neighbouring populations from Brazil. Six mtDNA CR haplotypes were identified in Brazil with no sharing between the two populations, as well as specific cytochrome b (cyt b) haplotypes identified in each locality. In addition, we analyzed autosomal microsatellites to investigate male-mediated gene flow and demographic changes within the study area in Brazil. Data analysis of 14 microsatellite loci failed to detect significant population subdivision, suggesting that male-mediated gene flow may maintain homogeneity between these two locations. Moreover, both mtDNA and microsatellite data indicate a major demographic collapse within Brazil in the late Pleistocene. Bayesian skyline plots (BSP) of mtDNA data revealed a stable population for Colombian and Brazilian Amazon lineages through time, whereas a population decline was demonstrated in the Colombian Orinoco lineage. Moreover, BSP and Tajima's D and Fu's Fs tests revealed a recent population expansion exclusively in the Bolivian sample. Finally, we estimated that the diversification of the Inia sp. lineage began in the Late Pliocene (approximately 3.

Phylogeographical patterns shed light on evolutionary process in South America

“…; Hollatz et al . ). Possible reasons for discordant patterns between markers include differences in the dispersal patterns of males and females (Eizirik et al .…”

“…; Hollatz et al . ); differences between pollen vs. seed dispersal rates (Caetano et al . ; Palma‐Silva et al .…”

Phylogeography and Sex-Biased Dispersal across Riverine Manatee Populations (Trichechus inunguis and Trichechus manatus) in South America

“…If females were dispersing, lack of structure between populations would be expected when analyzing mitochondrial and microsatellite data, while male dispersal and female philopatry would show population structure for mitochondrial data, but none or lesser levels of structure for microsatellites data, as has been reported for other aquatic mammals (i.e., Amazon river dolphin [ Inia geoffrensis ], Hollatz et al 2011; sperm whales [ Physeter macrocephalus ], Lyrholm et al 1999; dusky dolphins [ Lagenorhynchus obscurus ], Cassens et al 2005; and Dall’s porpoise [ Phocoenoides dalli ], Escorza-Treviño & Dizon 2000 [57], [58], [59], [60]). Microsatellite data presented high homozygote frequencies for all populations of T. manatus and T. inunguis , which supported the presence of null alleles and deviations from HWE.…”

Walking in a heterogeneous landscape: Dispersal, gene flow and conservation implications for the giant panda in the Qinling Mountains

“…However, the shape of this relationship may be complex. Many empirical studies have demonstrated that dispersal can be impeded by significant biotic (e.g., behavioural) and/or abiotic (e.g., physical) barriers (Hollatz et al., ; Vallinoto et al., ). These boundaries may result in fine‐scale genetic structure within populations and which is consistent with the hypothesis of isolation‐by‐barriers (IBB).…”

“…However, the shape of this relationship may be complex. Many empirical studies have demonstrated that dispersal can be impeded by significant biotic (e.g., behavioural) and/or abiotic (e.g., physical) barriers (Hollatz et al, 2011;Vallinoto et al, 2006).…”