Intrinsic rate of increase,body size,and specific metabolic rate in marine mammals

Summary Hennemann (1983) provided empirical support for McNab's (1980) hypothesis that a higher specific metabolic rate (SMR) in mammals translates into a higher intrinsic rate of increase (r _m ). However, the few marine mammals in Hennemann's data base were excluded from any detailed analyses because their high rates of metabolism but only average or low values of r _m (p. 106) were thought to reflect trade-offs between maintenance and production necessary to compensate for heat loss in aquatic environments (Hennemann 1983, also see McNab 1980).To investigate further the relationships among r _m , body size, and specific metabolic rate in marine mammals (pinnepeds, sirenians, and cetaceans), r _m was estimated for 37 populations using published life-history data and Cole's (1954) equation (Hennemann 1983). Estimates of r _m in relation to body size in marine mammals were generally within the 95% confidence limits calculated for terrestrial mammals using Hennemann's data. Contrary to Hennemann's (1983) observations, eight of these populations had an r _m which was higher in relation to body size than predicted by the average terrestrial mammalian relationship. Furthermore, for marine mammal populations where suitable data were available, r _m was correlated with specific metabolic rate (r=0.85, P0.035) and all the estimates were again within the 95% confidence limits established from data for terrestrial mammals (Hennemann 1983). It is premature, therefore, to reject the hypothesis that marine mammals do not differ significantly from terrestrial mammals in their allocation of energy for maintanance and reproduction.     

Body size,duration of parental care,and the intrinsic rate of natural increase in eutherian and metatherian mammals

Summary The intrinsic rate of natural increase (r _m), conception to weaning time (t _cw), age of first reproduction (t_mat), and components of fecundity were compared between ecologically similar groups of 42 metatherian (=marsupial) and 42 eutherian mammals. Marsupial t _cw s average 50% longer than those of eutherians. Small marsupials (<400 g) mature later, and have lower and r _ms than eutherians; large marsupials (>10,000 g) do not mature later but also have lower r _ms. At body sizes of 1,000–3,500 g, marsupials and eutherians have similar t _mat s and t _cw s but marsupials have greater r _ms. Marsupials compensate for their longer t _cw s by a variety of methods including embryonic diapause, larger litter sizes, and short periods between weaning and maturity. Although the greatest similarities in marsupial and eutherian life histories are at body sizes of 1–5 kg, compensation for long t _cw may be seen at any marsupial body size. Other ecological factors not withstanding, marsupial reproduction is neither inherently inferior to that of eutherians nor obviously more advantageous in unpredictable environs.     

The macroevolutionary relationship between diet and body mass across mammals

Body mass and diet are two fundamental ecological parameters that influence many other aspects of an animal's biology. Thus, the potential physiological and ecological processes linking size and diet have been the subject of extensive research, although the broad macroevolutionary relationship between the two traits remains largely unexplored phylogenetically. Using generalized Ornstein–Uhlenbeck models and data on over 1350 species of mammal, we reveal that evolutionary changes in body mass are consistently associated with dietary changes across mammals. Best‐fitting models find that herbivores are substantially heavier than other dietary groups and that omnivores are frequently intermediate in mass between herbivores and carnivores. Interestingly, although flying and swimming both place very different physical constraints on mass, bats still follow the general mammalian pattern but marine mammals do not. Such differences may be explained by reduced gravitational constraints on size in water along with ecological differences in food availability between aquatic and terrestrial realms, allowing marine carnivores to become the largest mammals on earth. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 173–184.     

Intrinsic rate of natural increase of Brueelia amandavae (Ischnocera, Phthiraptera) populations infesting Indian red avadavat

The incubation period of eggs, duration of three nymphal instars, adult longevity and the daily egg-deposition rate of the ischnoceran Phthiraptera, Brueelia amandavae, were determined by rearing the louse in vitro (35 ± 1°C, 75–82% RH, feather diet). The data obtained were utilized for life table construction and determination of the intrinsic rate of natural increase (0.031 per day) and the doubling time (23.45 days) of the louse population. The doubling time of the louse in in vivo experiments was 21.5 days.     

The intrinsic rate of natural increase and reproductive effort in primates

The intrinsic rate of natural increase (r_max) is calculated for 58 primate species. It is found that this parameter is negatively correlated with body weight, so that larger primate species consistently have a lower r_max than do smaller species. Although there is no apparent link between the raw value of r_max and environmental predictability, a relationship between a high r_max, relative to body weight, and an unpredictable environment is found to exist. However, there is no relationship between a predictable environment and either the raw value of r_max, or the relative r_max. After body size effects are removed, r_max is not correlated with basal metabolic rate (BMR). Pre-natal maternal investment (MI) is found to correlate highly with BMR, even after the removal of body weight effects. MI does not correlate either with r_max or with environmental predictability. Diet appears to have little influence either on r_max on MI, but there is some indication that folivores have both a high relative r_max and a high relative MI. These results are discussed in the light of theories of life-history strategy evolution.     

Feeding innovations in a nested phylogeny of Neotropical passerines

Several studies on cognition, molecular phylogenetics and taxonomic diversity independently suggest that Darwin''s finches are part of a larger clade of speciose, flexible birds, the family Thraupidae, a member of the New World nine-primaried oscine superfamily Emberizoidea. Here, we first present a new, previously unpublished, dataset of feeding innovations covering the Neotropical region and compare the stem clades of Darwin''s finches to other neotropical clades at the levels of the subfamily, family and superfamily/order. Both in terms of raw frequency as well as rates corrected for research effort and phylogeny, the family Thraupidae and superfamily Emberizoidea show high levels of innovation, supporting the idea that adaptive radiations are favoured when the ancestral stem species were flexible. Second, we discuss examples of innovation and problem-solving in two opportunistic and tame Emberizoid species, the Barbados bullfinch Loxigilla barbadensis and the Carib grackle Quiscalus lugubris fortirostris in Barbados. We review studies on these two species and argue that a comparison of L. barbadensis with its closest, but very shy and conservative local relative, the black-faced grassquit Tiaris bicolor, might provide key insights into the evolutionary divergence of cognition.     

Assemblage-level responses of Neotropical bats to forest loss and fragmentation

Habitat loss and fragmentation are the most important causes of biological diversity loss, changing the properties of the remaining environment. The Neotropical Region is one of the most affected areas due to the conversion of natural habitats into agricultural activities and deforestation. In this region, bats represent almost 50% of all mammal species, reaching the highest taxonomic and functional diversity. Bats are valuable indicators of biodiversity and ecosystem health, but their response to habitat loss and fragmentation was poorly studied in Argentina. The aim of this study was to analyze the response of bat assemblages to habitat alteration in Northwestern Argentina. The specimens were collected in eight different localities, four well-preserved and four disturbed sites of the Yungas Forests. To describe the structure of bat assemblages, rank-abundance curves, species richness and Shannon (H’) and Simpson (D’) diversity indexes were calculated. To test the assemblage variations among sites, PCA and NPMANOVA analysis were performed. After 96 sampling nights, a total of 565 bats from 23 species were captured. A great variation in the assemblage structure was registered, regardless the disturbance level of the sites. These variations were not significantly different according to statistical analysis. The results support the hypothesis that areas with moderate fragmentation can sustain a high diversity of bat species. Moreover, these results showed that consistent responses to landscape composition at the assemblage level are harder to identify in fragmented Neotropical Forests. The responses of bats to habitat alteration tend to be highly species-specific.     

Basal metabolic rate in carnivores is associated with diet after controlling for phylogeny

Studies of basal metabolic rate (BMR), the minimum metabolic rate of postabsorptive, inactive endotherms while in their rest phase and thermal neutral zone, have contributed significantly to our understanding of animal energetics. Besides body mass, the main determinant of BMR, researchers have invoked diet and phylogenetic history as important factors that influence BMR, although their relative importance has been controversial. For 58 species within the Carnivora, we tested the hypothesis that BMR is correlated with home range size, a proxy for level of activity, and diet, using conventional least squares regression (CLSR) and regression based on phylogenetic independent contrasts (PIC). Results showed that BMR of Carnivora was positively correlated with home range size after controlling for body mass, regardless of the statistical method employed. We also found that diet and mass-adjusted home range size were correlated. When we simultaneously tested the effect of diet and mass-adjusted home range on mass-adjusted BMR, home range size was insignificant because of its colinearity with diet. Then we eliminated home range size from our model, and diet proved to be significant with both CLSR and PIC. We concluded that species that eat meat have larger home ranges and higher BMR than species that eat vegetable matter. To advance our understanding of the potential mechanisms that might explain our results, we propose the "muscle performance hypothesis," which suggests that selection for different muscle fiber types can account for the differences in BMR observed between meat eaters and vegetarian species within the Carnivora.     

Inverse relationship between longevity and evolutionary rate of mitochondrial proteins in mammals and birds

Recently, an unexpected, positive correlation between the rate of evolution of mitochondrial proteins and longevity was reported. Here we re-analyze this relationship in various mammalian lineages using a bayesian phylogenetic analysis of amino-acid sequences, allowing for variable evolutionary rates across sites and species. A negative relationship between protein evolutionary rate and species longevity is reported for all oxidative phosphorylation complexes. A detailed analysis of the cytochrome b in 528 mammals reinforced this result, which contradicts previous publications. Reconducting the analysis in birds yielded similar results. We explain the discrepancy between this and previous reports by our improved taxon sampling and more appropriate methodology: unlike distance-based methods, the tree-based bayesian approach can take into account the high variation of substitution rate across amino-acid sites, and the resulting multiple substitution events. We discuss how our analysis contradicts Rottenberg’s rationale, but does not dismiss his proposal of a longevity-dependent selective pressure on mitochondrial mutation rate in mammals and birds. This is because his interpretation invokes adaptation as the single evolutionary force at work, disregarding the effects of mutation, genetic drift, and purifying selection.     

Comparing iDNA from mosquitoes and flies to survey mammals in a semi-controlled Neotropical area

Ingested-derived DNA (iDNA) from insects represents a powerful tool for assessing vertebrate diversity because insects are easy to sample, have a diverse diet and are widely distributed. Because of these advantages, the use of iDNA for detecting mammals has gained increasing attention. Here we aimed to compare the effectiveness of mosquitoes and flies to detect mammals with a small sampling effort in a semi-controlled area, a zoo that houses native and non-native species. We compared mosquitoes and flies regarding the number of mammal species detected, the amount of mammal sequence reads recovered, and the flight distance range for detecting mammals. We also verified if the combination of two mini-barcodes (12SrRNA and 16SrRNA) would perform better than either mini-barcode alone to inform local mammal biodiversity from iDNA. To capture mosquitoes and flies, we distributed insect traps in eight sampling points during 5 days. We identified 43 Operational Taxonomic Units from 10 orders, from the iDNA of 17 mosquitoes and 46 flies. There was no difference in the number of species recovered per individual insect between mosquitoes and flies, but the number of flies captured was higher, resulting in more mammal species recovered by flies. Eight species were recorded exclusively by mosquitoes and 20 by flies, suggesting that using both samplers would allow a more comprehensive screening of the biodiversity. The maximum distance recorded was 337 m for flies and 289 m for mosquitoes, but the average range distance did not differ between insect groups. Our assay proved to be efficient for mammal detection, considering the high number of species detected with a reduced sampling effort.     

Environmental correlates of the intrinsic rate of natural increase in primates

Morphological and life history traits of two clones of the cladoceran Daphnia pulex were measured in the presence and absence of size-selective insect predators, the midge larva Chaoborus flavicans, which preys on small Daphnia, and the water bug Notonecta glauca, which preys on large Daphnia. The aim was to detect predator-induced phenotypic changes, particularly the effect of simultaneous exposure to both types of predators. Other work has shown that in the presence of Chaoborus americanus, Daphnia pulex produce a socalled neck spine which may carry several teeth. The morphological modifications are supposed to serve as an anti-predator device. Furthermore, females exposed to Chaoborus often delay their maturation; this has been interpreted as a cost that balances the benefits of the neck teeth. In this investigation, females of both clones produced fewer but larger offspring than control animals when reared in the presence of Chaoborus flavicans. The offspring showed the typical neck spine and delayed first reproduction. In the presence of Notonecta glauca, one of the clones produced more and smaller offspring, and maturation occurred at earlier instars. The other clone also produced more offspring than the control but there was no size difference. When both predators were present, in most cases the reactions of the daphnids were similar to those in the Notonecta experiment. The response to Chaoborus appeared to be suppressed. The observed modifications are interpreted as evolved strategies that reduce the impact of size-selective predation. They are consistent with predictions of life-history theory.     

A true rate of population growth--Lotka's intrinsic rate of natural increase revisited.

In this paper, Lotka's intrinsic rate of current population growth is evaluated. A new method of computing the net reproduction rate and a new rate of population growth are proposed. The proposed rate is the rate of growth of the female population per woman per year. The rate is positive, equal to zero, or negative as a population is increasing, remaining stationary, or decreasing. The rate for the 1987 U.S. white female population was R = -0.0037. This means that the white population was decreasing in 1987 and was losing 3.7 females for every 1000 women per year.     

Allometry of thermal variables in mammals: consequences of body size and phylogeny

A large number of analyses have examined how basal metabolic rate (BMR) is affected by body mass in mammals. By contrast, the critical ambient temperatures that define the thermo‐neutral zone (TNZ), in which BMR is measured, have received much less attention. We provide the first phylogenetic analyses on scaling of lower and upper critical temperatures and the breadth of the TNZ in 204 mammal species from diverse orders. The phylogenetic signal of thermal variables was strong for all variables analysed. Most allometric relationships between thermal variables and body mass were significant and regressions using phylogenetic analyses fitted the data better than conventional regressions. Allometric exponents for all mammals were 0.19 for the lower critical temperature (expressed as body temperature ‐ lower critical temperature), ?0.027 for the upper critical temperature, and 0.17 for the breadth of TNZ. The small exponents for the breadth of the TNZ compared to the large exponents for BMR suggest that BMR per se affects the influence of body mass on TNZ only marginally. However, the breadth of the TNZ is also related to the apparent thermal conductance and it is therefore possible that BMR at different body masses is a function of both the heat exchange in the TNZ and that encountered below and above the TNZ to permit effective homeothermic thermoregulation.