RESUMO
Vicuñas and guanacos are two species of wild South American camelids that are key ruminants in the ecosystems where they occur. Although closely related, these species feature differing ecologies and life history characters, which are expected to influence both their genetic diversity and population differentiation at different spatial scales. Here, using mitochondrial and microsatellite genetic markers, we show that vicuña display lower genetic diversity within populations than guanaco but exhibit more structure across their Peruvian range, which may reflect a combination of natural genetic differentiation linked to geographic isolation and recent anthropogenic population declines. Coalescent-based demographic analyses indicate that both species have passed through a strong bottleneck, reducing their effective population sizes from over 20,000 to less than 1000 individuals. For vicuña, this bottleneck is inferred to have taken place ~3300 years ago, but to have occurred more recently for guanaco at ~2000 years ago. These inferred dates are considerably later than the onset of domestication (when the alpaca was domesticated from the vicuña while the llama was domesticated from the guanaco), coinciding instead with a major human population expansion following the mid-Holocene cold period. As importantly, they imply earlier declines than the well-documented Spanish conquest, where major mass mortality events were recorded for Andean human and camelid populations. We argue that underlying species' differences and recent demographic perturbations have influenced genetic diversity in modern vicuña and guanaco populations, and these processes should be carefully evaluated in the development and implementation of management strategies for these important genetic resources.
Assuntos
Camelídeos Americanos/genética , Demografia , Variação Genética , Genética Populacional , Animais , Chile , Análise por Conglomerados , DNA Mitocondrial , Frequência do Gene , Loci Gênicos , Marcadores Genéticos , Haplótipos , Repetições de Microssatélites , PeruRESUMO
Histopathological analysis of 108 intestine samples (103 grossly affected ileum and 5 jejunum) taken from Clostridium-induced neonatal alpaca (Vicugna pacos) enterotoxemia mortalities collected in the Departments of Arequipa, Puno and Cusco of southern Peru during the 2005-2008 birth seasons (January-March), revealed the presence of large numbers of both asexual and sexual stages of Eimeria macusaniensis in 33/108 (30.55%) of the samples with moderate to severe necrotized and/or hemorrhagic enteritis. It is proposed that damage to the mucosa produced by coccidial infections may facilitate overgrowth of Clostridium perfringens with toxin production leading to fatal enterotoxemia.
Assuntos
Animais Recém-Nascidos , Camelídeos Americanos , Coccidiose/veterinária , Eimeria/fisiologia , Enterotoxemia/complicações , Enterotoxemia/patologia , Animais , Clostridium perfringens/crescimento & desenvolvimento , Coccidiose/complicações , Coccidiose/patologia , Conteúdo Gastrointestinal/química , Conteúdo Gastrointestinal/microbiologia , Conteúdo Gastrointestinal/parasitologiaRESUMO
The vicuña (Vicugna vicugna; Miller, 1924) is a conservation success story, having recovered from near extinction in the 1960s to current population levels estimated at 275,000. However, lack of information about its demographic history and genetic diversity has limited both our understanding of its recovery and the development of science-based conservation measures. To examine the evolution and recent demographic history of the vicuña across its current range and to assess its genetic variation and population structure, we sequenced mitochondrial DNA from the control region (CR) for 261 individuals from 29 populations across Peru, Chile and Argentina. Our results suggest that populations currently designated as Vicugna vicugna vicugna and Vicugna vicugna mensalis comprise separate mitochondrial lineages. The current population distribution appears to be the result of a recent demographic expansion associated with the last major glacial event of the Pleistocene in the northern (18 to 22 degrees S) dry Andes 14-12,000 years ago and the establishment of an extremely arid belt known as the 'Dry Diagonal' to 29 degrees S. Within the Dry Diagonal, small populations of V. v. vicugna appear to have survived showing the genetic signature of demographic isolation, whereas to the north V. v. mensalis populations underwent a rapid demographic expansion before recent anthropogenic impacts.