Spatial genetic structure of two sympatric neotropical palms with contrasting life histories

The spatial genetic structure within sympatric populations of two neotropical dioecious palm species with contrasting life histories was characterized to evaluate the influence of life history traits on the extent of genetic isolation by distance. Chamaedorea tepejilote is a common wind-pollinated arboreal understory palm. Chamaedorea elatior is an uncommon climbing subcanopy palm with entomophilous pollination syndrome. A total of 59 allozyme alleles for C. tepejilote and 53 alleles for C. elatior was analyzed using both unweighted (Iu) and weighted (Iw) Moran's I spatial autocorrelation statistics. The spatial genetic structure detected within these populations is consistent with those reported for highly dispersed plants. A significance test for differences between mean Moran's I-coefficients revealed less spatial genetic structure within the C. tepejilote population than that in the C. elatior population. Adjacent individuals of C. elatior exhibited significant spatial genetic autocorrelation (Iu=0.039, Iw=0.034), indicating a Wright's neighborhood size of about 100 individuals. For C. tepejilote, nonrandom genetic distribution among nearest neighbors was detected, even from small spatial autocorrelation values (Iu=0.008, Iw=0.009), consistent with a neighborhood size of about 300 individuals. For both species, seed dispersal, mortality among life cycle stages, overlapping generations, and contrasting traits of mating and reproduction influence the standing spatial genetic structure within populations.     

Early life histories of three sympatric sticklebacks in a salt-marsh

The effects of abiotic factors (water level, temperature, dissolved oxygen and salinity) and interspecific competition on the survival and growth of early life stages of three sympatric sticklebacks, Gasterosteus aculeatus , G. wheallandi and Pungitius pungitius , were studied in salt-marsh tide pools near Isle Verte, Quebec. Significant year-to-year variation was observed in the percentage of live eggs per nest, egg incubation times, and the growth and condition of juveniles for all three species. These differences were associated with variations in temperature, oxygen and salinity in the pools. Comparisons of egg survival and juvenile growth rates were also made for G. aculeatus living in two contrasting habitats of the salt-marsh, the harsh and variable tide pools, and a less harsh, less variable freshwater site. Egg incubation times were longer, and the percentage of live eggs per nest lower, in the river than in the pools. However, river juveniles had higher growth rates and condition factors than pool juveniles. Results of experiments to study interspecific competition between juvenile G. aculaetus and juvenile G. wheatlandi were inconsistent, and it is suggested that the effects of abiotic factors on the survival and growth of early life stages in sticklebacks are more important than competition at this site.     

Inter- and intraspecific variation in the life histories of three sympatric isopods in a Hong Kong forest

There is a paucity of data on the life-history strategies of tropical animals. Accordingly, the inter and intraspecific life-history variations of three sympatric isopods, Burmoniscus oceliutus (Philosciidae), Formosillo raffaelei and Orodillo maculatus (Armadillidae), were studied at two sites in a Hong Kong forest. All three isopods were iteroparous. Burmoniscus oceilutus had more frequent breeding bouts, and smaller broods than O. muculutus and F. raffaelei. Although the three isopods had different life spans, brood numbers and life-time fecundities, their rates of offspring production (number of eggs per month) were similar. The Hong Kong isopods had longer breeding periods, a greater number of broods per life time, and lower reproductive allocation per brood than their temperate counterparts. These findings were consistent with the predictions of r - and K-theory. Intraspecific, between-site differences in fecundity and brood dry weight of F. raffaelei could probably be explained by the variations in the size of gravid females. Burmoniscus ocellutus produced heavier eggs at the site with a higher population density, suggesting that conditions at the site with a higher isopod density may be more K-selecting. Female-biased sex ratios, possibly resulting from differential sex-specific mortality, were common among the isopod samples, and the possible adaptive significance of this pattern was discussed. The potential influence of phylogenetic constraints on the evolution of life-history strategies was also considered.     

Geographical patterns of genetic structure in marine species with contrasting life histories

Aim  Phylogeographical breaks may reflect historical or present-day impediments to gene flow, and the congruence of these breaks across multiple species lends insight into evolutionary history and connectivity among populations. In marine systems, examining the concordance of phylogeographical breaks is challenging due to the varied sampling scales in population genetics studies and the diverse life histories of marine organisms. A quantitative approach that considers the effects of sampling scale and species life history is needed.
Location  The south-east and south-west coasts of the United States.
Methods  We quantitatively analysed previously published datasets of marine fauna to look for concordance among phylogeographical breaks. We used a bootstrap approach to determine the regions where phylogeographical breaks are more common than expected by chance among species with planktonic dispersal as well as those with restricted dispersal.
Results  On the south-west coast, breaks were clustered near Point Conception among planktonic dispersers and near Los Angeles among restricted dispersers. On the south-east coast, breaks were most common near the southern tip of Florida for planktonic dispersers and near Cape Canaveral for restricted dispersers.
Main conclusions  Dispersal ability is an important determinant of phylogeographical patterns in marine species. Breaks among planktonic dispersers on both coasts are congruent with present-day flow-mediated barriers to dispersal, suggesting that phylogeographical structure in species with planktonic larvae may reflect contemporary oceanography, while breaks in restricted dispersers reflect historical processes. These results highlight the importance of explicitly considering sampling scale and life history when evaluating phylogeographical patterns.     

Hierarchical genetic structure and gene flow in three sympatric species of Amazonian rodents

The population genetic structure of three species of Amazonian rodents ( Oligoryzomys microtis, Oryzomys capito , and Mesomys hispidus ) is examined for mtDNA sequence haplotypes of the cytochrome b gene by hierarchical analysis of variance and gene flow estimates based on fixation indices ( N _ST) and coalescence methods. Species samples are from the same localities along 1000 km of the Rio Juruá in western Amazonian Brazil, but each species differs in important life history traits such as population size and reproductive rate. Average haplotype differentiation, hierarchical haplotype apportionment, and gene flow estimates are contrasted in discussing the current and past population structure. Two species exhibit isolation by distance patterns wherein gene flow is largely limited to geographically adjacent localities. Mesomys exhibits this pattern throughout its range along the river. More than 75% of haplotype variation is apportioned among localities and regions, and estimates of Nm for pair-wise comparisons are nearly always less than 1. Oligoryzomys shows weak isolation by distance, but only over the largest geographical distances. Nm values for this species are nearly always above 1 and most (about 80%) of haplotype variation is contained within local populations. In contrast, Oryzomys exhibits no genetic structure throughout its entire distribution; Nm values average 17 and nearly 90% of the total haplotype variance is contained within local populations. Although gene flow estimates are high, the pattern of Nm as a function of geographical distance suggests that this species experienced a more recent invasion of the region and is still in genetic disequilibrium under its current demographic conditions.     

Comparative life histories and microhabitat use in three sympatric sculpins (Cottidae:Cottus) in northeastern California

Synopsis Life histories of three sculpins endemic to the Pit River system, northeastern California, are detailed.Cottus pitensis is widely distributed throughout the drainage. This species is typically found in rapidly flowing, shallow water on coarse substrate. It grows to a large size, >100 mm, and lives to 5 years. Spawning occurs annually, in early spring. Fecundity is relatively low, <320 oocytes.Cottus asperrimus is restricted to a large population in Fall River and smaller concentrations in Hat Creek and Pit River. It is a relatively small fish, <80 mm, and lives to 5 years. It occurs in deep, slow-moving, often spring-fed streams, typically on fine substrates. Spawning lasts from autumn to early spring. Males establish nests on hard substrates and guard several clutches of eggs. Fecundity ranges from 140–580 oocytes.Cottus klamathensis macrops is relatively rare in the drainage. The largest concentration is in the Hat Creek system, smaller populations exist in Fall River and Pit River. This sculpin is found on coarse substrate, often where aquatic vegetation is abundant. It is typically found in slow, relatively shallow water. It grows to >100mm and lives to 5 years. Males guard eggs during the short spawning season beginning in late winter. Fecundity in this species reaches a maximum of 650 oocytes. Life history strategies vary within the genus, yet the life histories of these sculpins are more similar to each other than they are to many of their congeners. This within-group similarity may have resulted from exposure of all three species to similar environmental pressures. This is predicted by life-history theory.     

A test of a competition model with reference to three species of small mammals in south-eastern Australia

This study tests the hypothesis that competition occurs in a community of three species of small mammals (Antechinus stuartii and A. swainsonii, Marsupialia; Rattus fuscipes, Rodentia) in south-eastern Australia. The hypothesis was tested by using a simple model of competition that is based on two premises: I. competition results in a negative numerical or a negative spatial association between species, and II. competition is more intense where the densities of the competing species are relatively high. The model combines both premises and predicts that measures of association between competing species will be more negative where the species exist at high population densities than derived from the model and applied to data gathered in two study areas with contrasting mean animal densities. There was no evidence of numerical association among the species (three tests), but evidence of negative spatial association (three tests our of four). These latter findings were consistent with the predictions of the model. All species preferred the same broad kinds of habitat (macrohabitat), but they segregated into smaller, finer grained patches (microhabitat) when their numbers were relatively high. Such segregation was more evident between the two species of marsupials than between either species of marsupial and the eutherian rat. These findings suggested that competition occurs by interference, and reinforce the idea that an understanding of the behaviour of individuals is important to understanding competition between species.     

Population extinction risks of three Neotropical small mammal species

The population persistence and extinction probabilities of three small mammal species were analyzed by estimating growth and extinction properties obtained from 10 years of live-trapping data at two different habitat types in semiarid Chile. We used a stochastic formulation with an exponential growth model known as a Wiener-drift process, out of which growth and extinction quantities were estimated. The rodent Phyllotis darwini showed the lowest rates of growth, and the lowest infinitesimal variances, whereas the opposite trend was found for the rodent Akodonolivaceus. The marsupial Thylamys elegans showed intermediate values for growth rates and infinitesimal variances. The rodent P. darwini showed the lowest extinction risk in the study site. We also detected spatial differences between mesic and xeric habitats in the growth rates of P. darwini and T. elegans, and in the extinction risks of the three species studied. Although the population growth of these three species can be approximated by purely stochastic processes, the introduction of density dependence through autoregressive log-linear models reduced the extinction times of all species analyzed. Received: 16 May 1997 / Accepted: 22 January 1998     

Phytophagous insect communities in the canopies of three Eucalyptus forest types in south-eastern Australia

Intensive sampling of tree canopies for phytophagous insects was carried out in three contrasting eucalypt forest types comprised of species widely distributed in sub-alpine forests in Victoria and New South Wales (Eucalyptus delegatensis, E. dives, and E. pauciflora). The number of phytophagous insects present in the canopies of these forest types was low, with a seasonal average of 20 individuals per kg of foliage (dry weight). Numbers were much lower than expected from past literature reporting‘chronically high’levels of defoliation in eucalypt forests. Microlepidoptera, Geometridae, Chrysomelidae, and Curculionidae were the major leaf-chewing groups recorded. Most sap-feeders were either leafhoppers (Cercopidae and Cicadellidae) or in the superfamily Fulgoroidea. Psyllidae and gall-making species were rare. Leafhoppers made up a very large portion of the phytophagous insect communities in each forest type, particularly in the E. dives forest. Microlepidoptera was the most commonly encountered defoliator group in all three forest types making up 33-44% of the total count. Non-phytophagous arthropods accounted for 44-48% of all individuals encountered. The density of insect defoliators was greater in the lower crown than upper crown. The E. dives canopy supported many more phytophagous insects per unit weight of foliage, as well as more per hectare, than the other two forest types. The greatest number of phytophagous species was also encountered in E. dives canopy. The E. delegatensis canopy supported the lowest number of phytophagous insects per unit weight of foliage as Well as numbers per hectare. Abundance of insect defoliators in the eucalypt forest types in this study was similar to published figures of insect defoliators in northern temperate forests.     

Species-specific traits predict genetic structure but not genetic diversity of three fragmented Afrotropical forest butterfly species

The Upper Guinean forests of Ghana, West Africa, are considered among the most threatened and fragmented in the world. Little is known about the genetic consequences of fragmentation on Ghana’s forest-associated species, but this genetic signature is generally expected to differ across species. We compared patterns of mtDNA cytochrome oxidase I (COI) variation of three Nymphalid forest butterfly species that differ with respect to their relative dispersibilities (Aterica galene: high habitat fidelity, low dispersal ability; Euphaedra medon: high habitat fidelity, strong dispersal ability; Gnophodes betsimena: relaxed habitat fidelity, low dispersal ability). Individuals were collected from two large forest reserves and five small sacred forest groves. Patterns of differentiation across species were broadly coincident with our predicted hierarchy of relative species dispersibility and suggested that genetic connectivity is most compromised by strict fidelity to forest habitat rather than by raw capacity for sustained flight. Connectivity was uncorrelated with geographic distance, but instead seemed best explained by urbanization and the sequential pattern of forest loss. Genetic diversity was dramatically different among species and not easily explained by either species-specific traits or effects of fragmentation. Aterica galene, the species most impacted by fragmentation, exhibited very high diversity, whereas G. betsimena, a broadly distributed, very common species, with relaxed habitat fidelity, was genetically depauperate. There was limited evidence of genetic erosion from the sacred groves despite these small forest patches accounting for less than 1–10 % of the total area of the forest reserves, which indicates these forest relics have high conservation value.     

Comparative nest survival of three sympatric loon species breeding in the Arctic

Identifying factors influencing nest survival among sympatric species is important for understanding and managing sources of variation in population dynamics of individual species. Three species of loons nest sympatrically in northern Alaska and differ in body size, life history characteristics, and population trends. We tested the effects of competition, nest site selection, and water level variations on nest survival of Pacific Gavia pacifica, yellow‐billed G. adamsii, and red‐throated loons G. stellata on the Arctic Coastal Plain in Alaska. Although overall nest survival rates did not differ between species, the factors influencing nest survival varied. Nest site selection influenced nest survival for Pacific and yellow‐billed loons, with both species having high nest survival when nesting on islands and peninsulas, likely due to a reduction in access by terrestrial predators. However, on mainland shorelines, Pacific loons had lower nest survival than yellow‐billed loons, and used a higher proportion of vegetation mats for nest sites suggesting that their smaller body size makes them less adept at nest defense. Nest site selection did not influence nest survival of red‐throated loons corresponding to our result of no nest site preferences by this species. Initiation date had a strong influence on nest survival for Pacific and yellow‐billed loons with nests laid earlier having higher survival. Pacific and yellow‐billed loon nests were susceptible to flooding due to precipitation, which contrasted with red‐throated loons that nest on smaller lakes with lower water level variations. Competition did not affect nest survival for any of the species likely due to most territorial encounters occurring prior to incubation. The only influence we found on red‐throated loon nest survival was differences among years. Our results indicate that loons chose nest sites based on predation risk and that factors influencing breeding success of closely related species may differ under similar breeding conditions.     

Contrasting life histories in neighbouring populations of a large mammal

Background

A fundamental life history question is how individuals should allocate resources to reproduction optimally over time (reproductive allocation). The reproductive restraint hypothesis predicts that reproductive effort (RE; the allocation of resources to current reproduction) should peak at prime-age, whilst the terminal investment hypothesis predicts that individuals should continue to invest more resources in reproduction throughout life, owing to an ever-decreasing residual reproductive value. There is evidence supporting both hypotheses in the scientific literature.

Methodology/Principal Findings

We used an uncommonly large, 38 year dataset on Alpine chamois (Rupicapra rupicapra) shot at various times during the rutting period to test these two hypotheses. We assumed that body mass loss in rutting males was strongly related to RE and, using a process-based approach, modelled how male relative mass loss rates varied with age. For different regions of our study area, we provide evidence consistent with different hypotheses for reproductive allocation. In sites where RE declined in older age, this appears to be strongly linked to declining body condition in old males. In this species, terminal investment may only occur in areas with lower rates of body mass senescence.

Conclusions/Significance

Our results show that patterns of reproductive allocation may be more plastic than previously thought. It appears that there is a continuum from downturns in RE at old age to terminal investment that can be manifest, even across adjacent populations. Our work identifies uncertainty in the relationship between reproductive restraint and a lack of competitive ability in older life (driven by body mass senescence); both could explain a decline in RE in old age and may be hard to disentangle in empirical data. We discuss a number of environmental and anthropogenic factors which could influence reproductive life histories, underlining that life history patterns should not be generalised across different populations.     

Comparative phylogeography of five sympatric Hypseleotris species (Teleostei: Eleotridae) in south-eastern Australia reveals a complex pattern of drainage basin exchanges with little congruence across species

Aim To determine biogeographical patterns in five closely related species in the fish genus Hypseleotris, and to investigate the relative roles of drainage divide crossings and movement during lowered sea levels between drainage basins and biogeographical provinces based on the phylogeographical patterns within the group. The high degree of overlap in the distributions and ecology of these species makes them ideal candidates for comparative phylogeographical study. Location Eastern, central and south‐eastern Australia. Methods A total of 179 Hypseleotris individuals were sequenced from 45 localities for the complete mitochondrial cytochrome b gene and the first 30 base pairs of the threonine transfer RNA for a total of 1170 bp. Phylogenetic relationships were hypothesized using parsimony and Bayesian analyses. Results Phylogenetic analysis resolves the five species into three clades. The first corresponds to the species Hypseleotris klunzingeri ( Ogilby, 1898 ); within it two clades are resolved, one consisting of individuals from the Eastern Province (EP), plus two eastern Murray‐Darling Province (MDP) localities, and the other including the remainder of the MDP localities, along with the Lake Eyre Basin (Central Australian Province, CAP) individuals. The other two clades include a mixed Hypseleotris galii ( Ogilby, 1898 )/Hypseleotris sp. 3 Murray‐Darling clade, with EP and MDP lineages mostly segregated and differentiations in populations spread along the EP, and a mixed Hypseleotris sp. 4 Lake's and Hypseleotris sp. 5 Midgley's clade, with two groups of MDP localities and two CAP lineages indicated, interspersed with EP lineages as well as those from the Northern Province. Main conclusions This study is broadly congruent with a previous analysis of Hypseleotris phylogeny, but the previously observed overall relationship of south‐eastern Australian provinces [EP(MDP+CAP)] was not confirmed and is more complicated than hitherto thought. This highlights the necessity of obtaining a sufficient number of sampling localities to identify potential connectivity between populations in order to demonstrate congruent biogeographical patterns. We identified many instances of drainage divide crossings, which were the major means of movement between provinces. Despite the commonness of movement across drainage divides, very few of these were found to be exactly congruent among the species. Most occurred in different places, or if in the same location, apparently at different times, or in at least one case, in opposite directions. Patterns of movement between adjacent coastal drainages were also found to be largely incongruent; when congruence was found the populations involved had quite different genetic divergences.     

Non-invasive genetic identification of small mammal species using real-time polymerase chain reaction

DNA identification of non-invasive samples is a potentially useful tool for monitoring small mammal species. Here we describe a novel method for identifying five small mammal species: wood mouse, bank vole, common shrew, pygmy shrew and water shrew. Species-specific real-time polymerase chain reaction primers were designed to amplify fragments of the mitochondrial cytochrome b gene from hair and scat samples. We also amplified nuclear DNA from scats, demonstrating their potential as a source of DNA for population genetic studies.     

Contrasting population genetic structure of two sympatric species of Anthurium (Araceae) along elevation in an Andean mountain forest

The topography of the tropical Andean forest is steep, resulting in physical conditions that change with the elevation, thus driving a high turnover of insect pollinator species over short distances, which may lead to localized gene dispersal, promoting genetic divergence between plant populations distributed along the elevation gradient. In this study, we characterized the population genetic structure of Anthurium caucanum and A. panduriforme, two closely related species that coexist along the elevation gradient in the Andean forest but differ in inflorescence size and abundance of flower visitors. The sampling of both species covered seven elevation bands, from 2,200 to 2,900 MASL. Five microsatellite loci were used to genotype the sampled individuals. Our results indicated that heterozygosity was high for both species. Genotypic richness was significantly lower for A. caucanum (G/N = 0.45) compared with A. panduriforme (G/N = 0.88), while population differentiation was strong for A. caucanum (F_st = 0.23) but low for A. panduriforme (F_st = 0.03). Assignment analysis suggested a low rate of immigration events for A. caucanum populations and a high gene flow between A. panduriforme populations. Based on the seed production of bagged inflorescences, A. caucanum demonstrated the ability to self-pollinate, while A. panduriforme was considered self-incompatible. In addition, genotypic richness decreased with elevation for A. caucanum. In summary, the contrasting population genetic structure of the two Anthurium species along the elevation gradient appear to be the result of different gene flow rates, mating systems, and life-history traits, such as clonal growth, flowering phenology, and density.     

Tackling intraspecific genetic structure in distribution models better reflects species geographical range

Genetic diversity provides insight into heterogeneous demographic and adaptive history across organisms’ distribution ranges. For this reason, decomposing single species into genetic units may represent a powerful tool to better understand biogeographical patterns as well as improve predictions of the effects of GCC (global climate change) on biodiversity loss. Using 279 georeferenced Iberian accessions, we used classes of three intraspecific genetic units of the annual plant Arabidopsis thaliana obtained from the genetic analyses of nuclear SNPs (single nucleotide polymorphisms), chloroplast SNPs, and the vernalization requirement for flowering. We used SDM (species distribution models), including climate, vegetation, and soil data, at the whole‐species and genetic‐unit levels. We compared model outputs for present environmental conditions and with a particularly severe GCC scenario. SDM accuracy was high for genetic units with smaller distribution ranges. Kernel density plots identified the environmental variables underpinning potential distribution ranges of genetic units. Combinations of environmental variables accounted for potential distribution ranges of genetic units, which shrank dramatically with GCC at almost all levels. Only two genetic clusters increased their potential distribution ranges with GCC. The application of SDM to intraspecific genetic units provides a detailed picture on the biogeographical patterns of distinct genetic groups based on different genetic criteria. Our approach also allowed us to pinpoint the genetic changes, in terms of genetic background and physiological requirements for flowering, that Iberian A. thaliana may experience with a GCC scenario applying SDM to intraspecific genetic units.     

Effects of temperature on life histories of three endangered Japanese diving beetle species

To elucidate population-increasing factors in the diving beetle Cybister tripunctatus lateralis (Fabricius) (Coleoptera: Dytiscidae) in Japan in recent years, life histories and oviposition patterns were compared among three endangered diving beetle species, Cybister brevis Aubé (qualified by the Japanese Red Data List as ‘near threatened’), Cybister chinensis Motschulsky (vulnerable), and C. tripunctatus lateralis (vulnerable). Oviposition in C. brevis, C. chinensis, and C. tripunctatus lateralis was observed from late April to mid-June, from late April to early July, and from late May to mid-August, respectively, under semi-outdoor conditions. There were no interspecies differences in total hatchling production during the reproductive season. In rearing experiments at various temperatures (20, 23, 25, 28, and 30 °C), the mortality of C. tripunctatus lateralis larvae was higher at 20 °C, and gradually lower with increasing temperature up to 30 °C. Adult body size of females in C. tripunctatus lateralis is larger than that of males but there were no significant differences among temperatures (25–30 °C). Cybister brevis had a higher emergence rate at 23–28 °C than at 20 and 30 °C. In C. brevis, the body size of adults reared at 25 or 28 °C was significantly larger than at other temperatures. Cybister chinensis did not differ in emergence rate and adult body size among the five temperature conditions. The developmental zero (i.e., the lower developmental threshold) from the first instar to adult emergence was 11.1 °C for C. brevis, 8.7 °C for C. chinensis, and 16.8 °C for C. tripunctatus lateralis. We speculate how the influence of global warming may have a positive impact on the growth and survival of C. tripunctatus lateralis.     

Fluxes of elements in rain passing through forest canopies in south-eastern Australia

The elemental content of rainfall (bulk deposition), throughfall and stemflow was measured inPinus radiata D. Don andEucalyptus forests in Gippsland, Victoria. Accessions in rainfall (mg m^–2 year^–1) averaged: organic-C 551, NO₃ ^–-N 96, NH₄ ⁺-N 62, total-N 303, K⁺ 382, Na⁺ 2250, Ca²⁺ 1170, and Mg²⁺ 678. The mean pH of rainfall was 5.9. Concentrations of all elements were greater in throughfall than in rainfall, and generally greater in stemflow than in throughfall. However, pH of pine throughfall was higher than that of rainfall, and pH of eucalypt throughfall was lower than that of rainfall. There was a net efflux of inorganic-N from pine crowns to rainfall, whilst in eucalypts there was generally net sorption of inorganic-N from rainfall. In both species organic-N was leached from the crowns and the net efflux of total-N from eucalypt crowns (50 mg m^–2 year^–1) averaged one-quarter of that in pines. Increases in the organic-C content of throughfall relative to rainfall in eucalypts were two to four times those in pines. Increases in the content of other elements in throughfall were comparable in pines and eucalypts and within the ranges K⁺ 615–1360, Na⁺ 480–-1840, Ca²⁺ 123–780 and Mg²⁺ 253–993 mg m^–2 year^–1. However, enrichment of Ca²⁺ may have been due to dust trapped in the canopies. Stemflow contributed significantly to the total amounts of elements reaching the forest floor in water.     

Habitat separation of sympatric Microcebus spp. in the dry spiny forest of south-eastern Madagascar

We investigated whether or not habitat structure contributes to the separation of two sister species of lemurs and their hybrids. For this, we studied Microcebus murinus and M. griseorufus along a continuous vegetation gradient where populations of the two species occur in sympatry or in allopatry. In allopatry, the two species are generalists without any sign of microhabitat selectivity. In sympatry, both species differed significantly and discriminated against certain habitat structures: M. murinus was found in microhabitats with larger trees than average while M. griseorufus utilized microhabitats with smaller trees. Hybrids between the two species did not show any significant discrimination for or against microhabitat structure and did not differ in their habitat utilization from either parent species. Both species can go into torpor and hibernation. M. griseorufus is seen more frequently during the cool dry season than M. murinus. We assume that M. murinus goes into extended torpor or hibernation more frequently than M. griseorufus. We interpret the different occurrence of large-sized trees in microhabitats of M. murinus as a prerequisite for M. murinus to be able to spend extended periods of time in tree holes that are isolated and allow hibernation at reduced temperature levels.