Geographic Variation in Populations of Microcebus murinus in Madagascar: Resource Seasonality or Bergmann's Rule?

Abstract

Gray mouse lemurs (Microcebus murinus) occur in western Madagascar from the evergreen littoral rain forests at the southern tip of the island to the seasonal dry deciduous forests of the west and northwest. The wide geographic distribution allows researchers to investigate whether ecogeographic variations reflect adaptations to ambient temperatures, as a proxy for constraints of thermoregulation, or to rainfall, as a proxy of food availability. We compared body mass, number of litters/yr, and longevity for 3 populations: 1 from the evergreen littoral rain forest of the south (Mandena: annual mean temperature 23 • C, 1600 mm rain/yr), 1 from the dry deciduous forest of the west (Kirindy/CFPF: 25 • C, 800 mm), and 1 from the dry deciduous forest of northwestern Madagascar (Ampijoroa: 27 • C, 1200 mm). Body mass decreases with increasing ambient temperature from south to north (Mandena > Kirindy/CFPF > Ampijoroa). The number of litters/yr was highest in the littoral rain forest (2 or 3 litters/yr) and decreased with decreasing rainfall (Mandena > Ampijoroa > Kirindy/CFPF). Life expectancy is lowest in the littoral forest (13% recaptures of mouse lemurs between years) and high (ca. 30-40% recaptures between years) in the dry forests (Mandena <Kirindy/CFPF and Ampijoroa). We postulate that constraints of thermoregulation result in the latitudinal gradient of body mass. Reduced resource 984 Lahann, Schmid, and Ganzhorn productivity or seasonality is reflected in differences in reproductive rates, which seemed to be traded off against longevity. Thus body mass, longevity, and reproductive parameters respond differently to ambient conditions.

Senescence or selective disappearance? Age trajectories of body mass in wild and captive populations of a small-bodied primate

“…As expected, the estimated lifespans of wild and captive M. murinus differ substantially: captive males live on average twice as long and females 50% longer than their wild counterparts. Such variation reflects highly plastic life histories that may have helped the species to adapt to the gradient of ambient temperatures found within its natural geographical distribution, and contribute to the proposed pace-of-life variation found across this range [69]. Our results concur with previous studies [39,40] that have found longer lifespan and lower AS rates in captivity than in nature.…”

Geogenetic patterns in mouse lemurs (genus Microcebus ) reveal the ghosts of Madagascar's forests past

“…Ongoing work from the past two decades has shown conclusively that although the morphological differences among species of mouse lemur can be subtle, their genetic and ecological differences are consistent with an evolutionary radiation that presently contains 24 described species (25,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46), with the basal diversification occurring as long ago as 9-10 Ma (47,48). Several studies have shown strong support for three deep lineages, one that contains M. murinus plus Microcebus griseorufus, another deeply diverged lineage represented by Microcebus ravelobensis, Microcebus danfossi, and Microcebus bongolavensis, and a third lineage that comprises all other mouse lemur species, including strong support for a distal subclade containing M. berthae, Microcebus rufus, and Microcebus myoxinus (41,43,44,49).…”

Physiological flexibility and acclimation to food shortage in a heterothermic primate

“…Extreme phenotypic plasticity is common among vertebrates that have evolved in unstable, energetically restrictive environments, such as those exposed to ENSO climatic anomalies (Canale and Henry, 2010). Under natural conditions, grey mouse lemurs are faced with harsher energetic constraints than in the laboratory; wild animals weigh 40% less than captive ones in the mid-winter (Lahann et al, 2006), food availability is lower and foraging is less efficient and exposes starving animals to predation. The lack of chronic stress (cf.…”