Ecological and demographic impacts of a recent volcanic eruption on two endemic patagonian rodents

Abstract

Catastrophic events can significantly impact the demographic processes that shape natural populations of organisms. However, linking the outcomes of such events to specific demographic parameters is often challenging due to a lack of detailed pre-event data. The eruption of the Puyehue-Cordon Caulle volcanic complex on 4 June 2011 had profound consequences for the biota of southwestern Argentina. Our long-term behavioral, ecological, and demographic studies of two species of tuco-tucos ( Ctenomys sociabilis and C . haigi ) that occur in the region most heavily impacted by ash fall from the eruption provided an unusual opportunity to assess the effects of this event on natural populations of mammals. The post-eruption density of the study population for each species was markedly reduced compared to pre-eruption values, with the relative magnitude of this reduction being greater for the group-living C . sociabilis . The more extensive data set for this species indicated that ash fall from the eruption altered the food resources available to these animals; differences in pre- and post-eruption stable isotope signatures for fur samples from C . sociabilis were consistent with observed changes in vegetation. Per capita female reproductive success was also reduced in this species during the first breeding season following the eruption. Based on our detailed demographic records for C . sociabilis , neither survival of yearling females from 2010 to 2011 nor the percentage of unmarked females in the study population in 2011 differed from pre-eruption values. Instead, the post-eruption decrease in population density for C . sociabilis appeared to reflect reduced within-population recruitment of juvenile females to the 2011 breeding population. Although the eruption did not result in the local extinction of either study population, the demographic consequences detected are likely to have impacted the effective sizes of these populations, creating important opportunities to link specific demographic parameters to previously reported decreases in genetic variability detected after this significant natural event.

Dramatic recent changes in small mammal assemblages from Northern Patagonia: A caution for paleoenvironmental reconstructions

“…These animals, which currently occur in mesic patches of grasses and open shrubs in Neuquén Province, Argentina (Tammone et al, 2012), were present at CdC until ~3000 years BP (temporal unit V), after which they appear to have gone locally extinct. Stable isotope analyses of modern and fossil specimens suggest that this species underwent a significant dietary shift from native grasses during the Holocene to the invasive herbaceous vegetation consumed by extant populations (Lacey et al, 2019; Takenaka et al, 2020). The decline in abundance of this species, however, began before European settlement of the region and appears to reflect a gradual loss of suitable habitat during the Middle Holocene as increasing rainfall led to an eastward shift in forested habitats (Tammone et al, 2018b).…”

The Crane Flies of Martinique, with the Description of Four New Species (Diptera, Tipuloidea)

“…As mentioned in the introduction, the significant impact of catastrophic events, such as volcanoes, on the demographic processes that shape natural populations could be potentially devastating when they are framed in small territories, as is the case of the islands of the Lesser Antilles volcanic arc. However, the impact of these events on flora and fauna is often difficult to assess, due to the lack of detailed data prior to the event itself [17]. Although the Réserve Biologique Intégrale des Pitons du Carbet might not have been directly affected by the recent eruptions of Mount Pelée in 1902 and 1932, presumably a long history of catastrophic events could be one of the causes of the high abundance of species with a wide range of distribution on naturally defaunated islands (to the detriment of populations of supposedly endemic species), especially in inaccessible natural areas, where low, or almost zero, anthropic activity has been demonstrated (Gelhaus, pers.…”

Group living in highland tuco-tucos (Ctenomys opimus) persists despite a catastrophic decline in population density

“…While long-term studies can be used to examine relationships between behavior and typical changes in density [21,23], abrupt catastrophic changes in population density offer important opportunities to evaluate the effects of more extreme fluctuations in this demographic parameter. Abrupt declines in density have been reported for multiple species following a variety of natural catastrophic events [24][25][26][27][28]. Although often unpredictable, such events provide potentially compelling information, particularly if the resulting densities fall outside the range of values typically experienced by members of a population.…”