The effects of productivity and seasonality on life history: comparing age at maturity among moose (Alces alces) populations

The productivity hypothesis in respect of an animal species’ geographical range predicts that whereas higher productivity at the equatorial periphery of a species’ range favours superior competitors, lower productivity at the centre of a species’ range favours high reproduction and reduced competitive traits. I test whether life‐history patterns follow this hypothesis, using demographic data from 15 Canadian moose (Alces alces) populations. Two models are contrasted; the first assumes that intraspecific variation in age at maturity is explained proximately by density and juvenile mortality. Age at maturity was found to increase with decreasing juvenile mortality (P = 0.01) and increasing density (P = 0.006). To test the productivity hypothesis, the second model additionally included primary productivity and seasonality as geographical explanatory variables that would ultimately influence age at maturity via juvenile mortality and density. Path analysis indicated that including productivity and seasonality improved the model predictions of variation in age at maturity (R_a² 0.56 and 0.85). In bivariate comparisons, seasonality was negatively associated (P = 0.01) with age at maturity. In the best model, however, primary productivity was the environmental variable that explained 25% of the variance in age at maturity, and forest cover replaced seasonality as an explanatory variable. The positive association between primary productivity and age at maturity is consistent with the productivity hypothesis. Relative to populations that lived at the centre of the species’ range (51°N), moose populations living in relatively high productivity and low seasonality environments (equatorial periphery of species’ range; 48°N) experienced less juvenile mortality, more variable year‐to‐year density, higher relative density and slower life history (slower growth rate, later age at maturity, lower fecundity).     

Diet shift response in round goby,Neogobius melanostomus,based on size,sex, depth,and habitat in the western basin of Lake Erie

This study examines the diet of the round goby (Neogobius melanostomus) in the western basin of Lake Erie. As an invasive benthic feeder, the round goby has the potential to affect smallmouth bass and other native species. Round goby (n = 100) were collected during summer 2011 and stomach contents were examined to determine diet patterns and possible ontogenetic diet shifts. Individual round goby were grouped by sex, size (small < 65 mm, large ≥ 65 mm), depth of habitat (shallow < 2 m, deep > 5 m), and habitat type (natural shallows, anthropogenically modified shallows, and deep waters). Gut fullness ranged from 10 to 100% with 23 stomachs presenting 100% fullness. Round goby consumed 27 different food items including abiotic (sand grains, gravel), floral (algae, fine leaved vascular plants), and fauna items. The Index of Relative Importance (IRI) and comparative z‐tests were used to assess correlations and differences. Two‐way z‐tests revealed a significant difference in mouth gape related to size (z = ?5.56377, P = 2.64e‐08), and habitat depth (z = 3.34262, P = 0.00083). A significant linear correlation was also found between mouth gape standardized by head length (HL) for both males (P = 2.63e‐9) and females (P = 1.3e‐4). Two‐way z‐tests also revealed a significant difference in gonadosomatic index (GSI) related to sex (z = 6.07727, P = 6.11248e‐10), but not size. A significant difference in gut fullness was also found related to sex (z = ?3.34743, P = 0.00082), habitat depth (z = 3.16336, P = 0.00156), and habitat type (z = ?2.7398, P = 0.00615). IRI values demonstrated a diet selective of veliger mussels (IRI = 2462.01), juvenile mussels (IRI = 1073.03), cladocerans (IRI = 4804.31), and chironomids (IRI = 1012.12). While previous studies have focused on round goby diet shifts from macroinvertebrates to bivalves, most studies did not evaluate changes in diet among multiple categories. Furthering knowledge of multiple aspects of goby diet may aid in developing management techniques to deter future round goby invasion.     

Migration strategies of sylviid warblers: chance patterns or community dynamics?

The effects of community dynamics in birds on the optimisation of their migratory strategies is a neglected area. For three years, we captured migrating warblers on autumn passage at a coastal site in western Britain. We used canonical correspondence analysis (CCA) to assess spatio‐temporal patterns of occurrence, and principal components analysis (PCA) to assess morphological variation. We calculated Euclidean distance in ordination and morphological space to assess separation between species pairs, and used Monte‐Carlo simulations to assess the probability of pattern occurring by chance.
Ordination revealed five species‐groups separated by habitat type and time of passage. Reed Warbler Acrocephalus scirpaceus and Sedge Warbler A. schoenobaenus (Group 1) occurred in wet habitats and peaked simultaneously. In drier habitats with scrub, a first wave of Blackcap Sylvia atricapilla (Group 2) significantly preceded Grasshopper Warbler Locustella naevia, Willow Warbler Phylloscopus trochilus, Whitethroat Sylvia communis and Lesser Whitethroat Sylvia curruca (Group 3), which in all but one case (Lesser Whitethroat) significantly preceded Garden Warbler Sylvia borin (Group 4); peak numbers of Chiffchaffs Phylloscopus collybita and a second wave of Blackcaps (Group 5) occurred later still. Age effects were found only in Acrocephalus, with adults peaking before juveniles.
For seven out of eight pairings within genera, separation in time of passage increased significantly in species that were morphologically similar. The only exception was Blackcap and Lesser Whitethroat which differed substantially in both passage time and morphology. Monte‐Carlo simulations showed that chance was unlikely to be responsible for ordination patterns, nor for inter‐specific variation in passage time and its relationship with species morphology.
These data provide annually consistent evidence that migrating sylviid warblers are separated ecologically by habitat use, time of passage and morphology: we cannot refute the hypothesis that community dynamics have influenced niche use and autumn migratory strategy. We call for further tests of the ‘migrant interaction’ hypothesis in other geographical locations and taxa, particularly where migrants are allopatric and interact ecologically only on migration.     

Association of Ant Predators and Edaphic Conditions with Termite Diversity in an Amazonian Rain Forest

Predation is a key determinant of prey community structure, but few studies have measured the effect of multiple predators on a highly diverse prey community. In this study, we asked whether the abundance, species richness, and species composition of a species‐rich assemblage of termites in an Amazonian rain forest is more strongly associated with the density of predatory ants or with measures of vegetation, and soil texture and chemistry. We sampled termite assemblages with standardized hand‐collecting in 30 transects arranged in a 5 km × 6 km grid in a terra firme Amazonian rain forest. For each transect, we also measured vegetation structure, soil texture, and soil phosphorus, and estimated the density of predatory ants from baits, pitfall traps, and Winkler samples. Seventy‐nine termite species were recorded, and the total density of predatory ants was the strongest single predictor of local termite abundance (r = ?0.66) and termite species richness (r = ?0.44). In contrast, termite abundance and species richness were not strongly correlated with edaphic conditions (¦r¦ < 0.01), or with the density of non‐predatory ants (r_abund = ?0.27; r_s = ?0.06). Termite species composition was correlated with soil phosphorus content (r = 0.79), clay content (r = ?0.75), and tree density (r = ?0.42). Assemblage patterns were consistent with the hypothesis that ants collectively behaved as generalist predators, reducing total termite abundance, and species richness. There was no evidence that ants behaved as keystone predators, or that any single termite species benefited from the reduction in the abundance of potential competitors.     

Microbial macroecology: highly structured prokaryotic soil assemblages in a tropical deciduous forest

Aim To assess the hypothesis that free‐living prokaryotes show a pattern of ‘no biogeography’ by examining the scaling of soil prokaryotic diversity and by comparing it with other groups’ biogeographical patterns. Location Two sites in the tropical deciduous forest of Chamela, Jalisco, on the western coast of Mexico. Methods We examined the diversity and distribution of soil prokaryotes in two 8 × 8 m quadrats divided in such manner that we could sample at four spatial scales. Restriction fragment length polymorphisms of 16S rRNA genes were used to define operational taxonomic units (OTUs) that we used in lieu of species to assess diversity. Results We found highly structured species assemblages that allowed us to reject multiple predictions of the hypothesis that soil bacteria show ‘no biogeography’. The frequency distribution of range size (measured as the occupancy of quadrats) of OTUs followed a hollow curve similar to that of vertebrates on continents. Assemblages showed high levels of beta diversity and a non‐random nested pattern of diversity. OTU diversity scaled with area followed a power function with slopes z = 0.42 and 0.47. Main conclusions We demonstrate a non‐ubiquitous dispersal for soil prokaryotes, which suggests a complex biogeography similar to that found for terrestrial vertebrates.     

Population genetic structure and demographic history of the lone star tick,Amblyomma americanum (Ixodida: Ixodidae): New evidence supporting old records

Range expansions are a potential outcome of changes in habitat suitability, which commonly result as a consequence of climate change. Hypotheses on such changes in the geographic distribution of a certain species can be evaluated using population genetic structure and demography. In this study we explore the population genetic structure, genetic variability, demographic history of, and habitat suitability for Amblyomma americanum, a North American tick species that is a known vector of several pathogenic microorganisms. We used a double digestion restriction site‐associated DNA sequencing technique (dd‐RAD seq) and discovered 8,181 independent single nucleotide polymorphisms (SNPs) in 189 ticks from across the geographic range of the species. Genetic diversity was low, particularly when considering the broad geographic range of this species. The edge populations were less diverse than populations belonging to the historic range, possibly indicative of a range expansion, but this hypothesis was not statistically supported by a test based on genetic data. Nonetheless, moderate levels of population structure and substructure were detected between geographic regions. For New England, demographic and species distribution models support a scenario where A. americanum was present in more northern locations in the past, underwent a bottleneck, and subsequently recovered. These results are consistent with a hypothesis that this species is re‐establishing in this area, rather than one focused on range expansion from the south. This hypothesis is consistent with old records describing the presence of A. americanum in the northeastern US in the early colonial period.     

Past and future demographic dynamics of alpine species: limited genetic consequences despite dramatic range contraction in a plant from the Spanish Sierra Nevada

Anthropogenic global climate change is expected to cause severe range contractions among alpine plants. Alpine areas in the Mediterranean region are of special concern because of the high abundance of endemic species with narrow ranges. This study combined species distribution models, population structure analyses and Bayesian skyline plots to trace the past and future distribution and diversity of Linaria glacialis, an endangered narrow endemic species that inhabits summits of Sierra Nevada (Spain). The results showed that: (i) the habitat of this alpine‐Mediterranean species in Sierra Nevada suffered little changes during glacial and interglacial stages of late Quaternary; (ii) climatic oscillations in the last millennium (Medieval Warm Period and Little Ice Age) moderately affected the demographic trends of L. glacialis; (iii) future warming conditions will cause severe range contractions; and (iv) genetic diversity will not diminish at the same pace as the distribution range. As a consequence of the low population structure of this species, genetic impoverishment in the alpine zones of Sierra Nevada should be limited during range contraction. We conclude that maintenance of large effective population sizes via high mutation rates and high levels of gene flow may promote the resilience of alpine plant species when confronted with global warming.     

Genome‐wide association studies identify susceptibility loci affecting respiratory disease in Chinese Erhualian pigs under natural conditions

Prevalence of swine respiratory disease causes poor growth performance in and serious economic losses to the swine industry. In this study, a categorical trait of enzootic pneumonia‐like (EPL) score representing the infection gradient of a respiratory disease, more likely enzootic pneumonia, was recorded in a herd of 332 Chinese Erhualian pigs. According to their EPL scores and the disease effect on weight gains, these pigs were grouped into controls (EPL score ≤ 1) and cases (EPL score > 1). The weight gain of the case group reduced significantly at days 180, 210, 240 and 300 as compared to the control group. The heritability of EPL score was estimated to be 0.24 based on the pedigree information using a linear mixed model. All 332 Erhualian pigs and their nine sire parents were genotyped with Illumina Porcine 60K SNP chips. Two genome‐wide association studies were performed under a generalized linear mixed model and a case–control model respectively. In total, five loci surpassed the suggestive significance level (P = 2.98 × 10^?5) on chromosomes 2, 8, 12 and 14. CXCL6, CXCL8, KIT and CTBP2 were highlighted as candidate genes that might play important roles in determining resistance/susceptibility to swine EP‐like respiratory disease. The findings advance understanding of the genetic basis of resistance/susceptibility to respiratory disease in pigs.     

Disturbance from traditional fire management in subalpine heathlands increases Afro‐alpine plant resilience to climate change

Species are often controlled by biotic factors such as competition at the warm edge of their distribution range. Disturbances at the treeline, disrupting competitive dominance, may thus enable alpine species to utilize lower altitudes. We searched for evidence for range expansion in grazed, fire‐managed Ethiopian subalpine Erica heathlands across a 25‐year chronosequence. We examined vascular plant composition in 48 plots (5 × 5 m) across an altitudinal range of 3,465–3,711 m.a.s.l. and analyzed how community composition changed in relation to increasing competition over time (using a Shade index based on Erica shrub height and cover) and altitude. Species‘ habitats and altitudinal ranges were derived from literature. Time since fire explained more variation (r² = .41) in species composition than altitude did (r² = .32) in an NMDS analysis. Community‐weighted altitudinal optima for species in a plot decreased strongly with increasing shade (GLM, Standardized Regression Coefficient SRC = ?.41, p = .003), but increased only weakly with altitude (SRC = .26, p = .054). In other words, young stands were dominated by species with higher altitudinal optima than old stands. Forest species richness increased with Log Shade index (SRC = .12, p = .008), but was unaffected by altitude (SRC = ?.07, p = .13). However, richness of alpine and heathland species was not highest in plots with lowest Shade index, but displayed a unimodal pattern with an initial increase, followed by a decrease when shading increased (altitude was not significant). Our results indicate that disturbance from the traditional patch burning increases the available habitat for less competitive high‐altitude plants and prevents tree line ascent. Therefore, maintaining, but regulating, the traditional land use increases the Afro‐alpine flora's resilience to global warming. However, this system is threatened by a new REDD+ program attempting to increase carbon storage via fire suppression. This study highlights the importance of understanding traditional management regimes for biodiversity conservation in cultural landscapes in an era of global change.     

Palaeodistribution modelling and genetic evidence highlight differential post‐glacial range shifts of a rain forest conifer distributed across a latitudinal gradient

Aim We examine the range expansion/contraction dynamics during the last glacial cycle of the late‐successional tropical rain forest conifer Podocarpus elatus using a combination of modelling and molecular marker analyses. Specifically, we test whether distributional changes predicted by environmental niche modelling are in agreement with (1) the glacial maximum contractions inferred from the southern fossil record, and (2) population genetic‐based estimates of range disjunctions and demographic dynamics. In addition, we test whether northern and southern ranges are likely to have experienced similar expansion/contraction dynamics. Location Eastern Australian tropical and subtropical rain forests. Methods Environmental niche modelling was completed for three time periods during the last glacial cycle and was interpreted in light of the known palynology. We collected 109 samples from 32 populations across the entire range of P. elatus. Six microsatellite loci and Bayesian coalescence analysis were used to infer population expansion/contraction dynamics, and five sequenced loci (one plastid and four nuclear) were used to quantify genetic structure/diversity. Results Environmental niche modelling suggested that the northern and southern ranges of P. elatus experienced different expansion/contraction dynamics. In the northern range, the habitat suitable for P. elatus persisted in a small refugial area during the Last Glacial Maximum (LGM, 21 ka) and then expanded during the post‐glacial period. Conversely, in the south suitable habitat was widespread during the LGM but subsequently contracted. These differential dynamics were supported by Bayesian analyses of the population genetic data (northern dispersal) and are consistent with the greater genetic diversity in the south compared with the north. A contact zone between the two genetically divergent groups (corresponding to the Macleay Overlap Zone) was supported by environmental niche modelling and molecular analyses. Main conclusions The climatic fluctuations of the Quaternary have differentially impacted the northern and southern ranges of a broadly distributed rain forest tree in Australia. Recurrent contraction/expansion cycles contributed to the genetic distinction between northern and southern distributions of P. elatus. By combining molecular and environmental niche modelling evidence, this unique study undermines the general assumption that broadly distributed species respond in a uniform way to climate change.     

When invasion may not be harmful: niche relations in a lizard assemblage

Some studies have suggested that non‐native species invasions may threaten local diversity by creating homogenized environments. However, many studies have been based on limited or anecdotal data, and/or have failed to consider the influence of habitat modification together with possible influences of non‐native species on native ones. Hemidactylus mabouia (Squamata, Gekkonidae) likely invaded natural environments in Brazil hundreds of years ago. Yet, little is known about whether it affects native lizard fauna. We tested whether H. mabouia negatively influences native lizard species richness and abundance on a regional scale and locally through niche overlap. We analyzed species abundance and richness of nine lizard assemblages, in five of which H. mabouia occurred. We evaluated niche overlap of species in a lizard assemblage with high H. mabouia abundance through null models. Niche axes included spatial use, temporal activity and diet. Although species abundance did not differ among sites with and without the invasive species, the presence of H. mabouia seems constrained to the richer assemblages sampled. We observed significantly higher niche overlap in spatial (?_obs = 0.63; ?_exp = 0.37; P_obs ≥ P_exp = 0.0002) and trophic axes (?_obs = 0.46; ?_exp = 0.17; P_obs ≥ P_exp < 0.001), but not in activity. When we considered all axes (three‐dimensional niche), there was no overlapping among the lizard species. Our findings did not support the hypothesis that this non‐native species negatively influences other sympatric lizard species.     

Population biology and vulnerability to fishing of deep‐water Eteline snappers

Deep‐water fish in the tropical and sub‐tropical Pacific Ocean have supported important fisheries for many generations. Observations of localised depletions in some fisheries have raised concerns about the sustainability of current fishing rates. However, quantitative assessments of deep‐water stocks in the Pacific region have been limited by the lack of adequate biological and fisheries data. Estimates are provided of age‐based demographic parameters for two important deep‐water snapper species in the Pacific, Etelis carbunculus and E. coruscans. A spawner biomass‐per‐recruit (SPR) model was applied to determine fishing mortality rates for each species that would achieve specified biological targets (40% unexploited levels, SPR₄₀) and limit (30% unexploited levels, SPR₃₀) reference points, and examine the sensitivity of the model to variation in natural mortality and age at first capture. The maximum observed age, based on increment counts from sectioned otoliths, was 21 years for E. carbunculus and 18 years for E. coruscans. Total mortality (Z), estimated from the Hoenig regression, was 0.21 year^?1 for E. carbunculus and 0.25 year^?1 for E. coruscans. The best approximating growth models were the von Bertalanffy model (L_∞ = 896 mm fork length, k = 0.28, t₀ = 0.51) for E. carbunculus and the logistic model (L_∞ = 879 mm fork length, k = 0.32 year^?1, t₀ = 3.42) for E. coruscans. The spawner biomass‐per‐recruit analysis demonstrated that lower rates of fishing mortality were required for E. coruscans than for E. carbunculus to maintain spawning biomass above estimated biological reference points. Estimates of spawner biomass‐per‐recruit were more sensitive to variation in natural mortality than in the age at first capture, suggesting that regulating fishing mortality rather than gear selectivity would be a more effective management measure for both species. Maintaining fishing mortality <0.1 for both species is recommended as a cautious approach to management, given the uncertainty in estimates of natural mortality and mixed fishery considerations.     

Do local moisture stress responses across tree species reflect dry limits of their geographic ranges?

Under future climate drought‐induced tree mortality may result in the contraction of species ranges and the reorganization of community composition where abundant and peripheral species exchange their patterns of dominance. Predicting these changes will be challenging because the future suitable habitat may be a mismatch for the current bioclimatic envelope because of discrepancies between the realized and fundamental niche. Here we evaluate the extent of the discrepancy, as applied to tree species in relation to their relative field‐recorded drought sensitivities and their observed range‐wide environmental moisture envelopes. The hypothesis tested was that different species levels of drought‐induced damage at sites where they co‐occur will be positively associated with the minimum moisture availability in the most drought‐prone part of each species current geographic range. We tested the hypothesis using drought damage measurements for 13 Australian Myrtaceae (including Eucalyptus) tree species at a site where all co‐occur, together with 120 years of climate data across their geographical ranges. With limited statistical power the results generated only modest support for the hypothesis suggesting limited capacity to predict future distributions under climate change scenarios. In spite of the poor dispersal capacities of Eucalyptus and allied genera, but consistent with knowledge of breeding systems and genetic variability within Eucalyptus, the findings also suggest that many species have a capacity for rapid adaptive response to climate change, including the vicissitudes of the late Quaternary.     

Deconstructing a controversial local range expansion: conservation biogeography of the painted reed frog (Hyperolius marmoratus) in South Africa

Local range expansions might either be the response of populations to climate or landscape change, or be caused directly by human intervention. In the latter case the expansion would be considered the first in the steps leading to a biological invasion. In species typically not the subject of human commerce, distinguishing the causes of local range expansions is problematic. Range dynamic theory provides a basis for doing so, and, when used to assess phylogeographical information, can be a powerful conservation biogeographical approach. Here we adopt this approach to resolve the controversial case of the recent range expansion of the painted reed frog (Hyperolius marmoratus) in southern South Africa. Within the last decade, H. marmoratus has spread westward approximately 500 km from its historical range. This local range expansion could either represent human‐mediated jump dispersal, or a response to landscape or climate change. To date, the latter has been assumed, although not universally. Using a phylogeographic approach to investigate these competing hypotheses, a portion of the mitochondrial COI gene was sequenced for individuals from within the historical range (n = 178), and four putatively introduced populations in dams (n = 121). There was substantial geographical population structure within the historical range, and these populations were significantly different from the dam populations (Φ_ST = 0.817, P < 0.001). The presence of one or a few dissimilar haplotypes in the dams suggests that introductions are from a number of different sources. This, in conjunction with new survey data, supports the hypothesis that recent establishment of these populations is the result of human‐mediated jump dispersal. The impact of this range expansion on ecosystem functioning is unknown, but given the rapid spread of this species and its potential influence on ecosystems, safeguards should be put in place to control further introductions and to restrict the currently invasive populations.     

Associations between the drill (Mandrillus leucophaeus) and sympatric monkeys in Korup National Park,Cameroon

Studies of polyspecific associations among African forest primates have primarily focused on arboreal Cercopithecus and Procolobus/Colobus species. We examined the association frequency of the terrestrial drill (Mandrillus leucophaeus) with six sympatric monkey species in Korup National Park, Cameroon, testing reports that Mandrillus associations are infrequent and transient. We conducted 3,284 km of trail walks for 12 months (February–June 2006; July 2007 to January 2008), recording species composition in 612 primate clusters. Using a Markov chain Monte Carlo test, we compared the observed frequency of dyadic associations against null models of “no association.” A novel conservative statistical approach which addresses possible dependence of observations close in time was also used, further strengthening confidence in our findings. Drills associated with all monkeys throughout the study period, and were with at least one other species (range 1–5) in half of the encounters. The association frequency of drills with red‐capped mangabeys (Cercocebus torquatus) was greater than expected by chance, which is interesting given the morphological adaptation of the Mandrillus‐Cercocebus clade for the exploitation of the same dietary niche, hard seeds. The difference we observed in the use of forest strata by drills and mangabeys may reflect a strategy to reduce food competition while in association. The nature and duration of observed drill associations varied. Although some associations seemed to be chance encounters, others lasted for hours with the involved species foraging together. Am. J. Primatol. 73:127–134, 2011. © 2010 Wiley‐Liss, Inc.     

Genetic variation in piñon pine, Pinus edulis, associated with summer precipitation

Three previous reports of microgeographical variation of glycerate dehydrogenase (Gly) frequencies in piñon, Pinus edulis, established the hypothesis that Gly frequencies contribute to adaptation to heterogeneous environments, specifically to variation in soil moisture. In each of these studies, the frequency of the Gly‐3 allele or of Gly‐33 homozygotes was higher on dry sites than on nearby moist sites. Here we attempt to extend these observations by testing the hypothesis that Gly frequencies respond to soil moisture variation on a range‐wide scale. Gly frequencies were surveyed in 11 natural populations, and the frequency of the Gly‐3 allele varied from 0.27 to 0.65 among the sample sites. Elevation varied from 1650 to 3100 m, and summer precipitation, defined as precipitation from April to August, varied from 13.7 to 26.4 cm. The soil types at the collection sites were schist, quaternary volcanic or a mixture of shale and sandstone. Logistic regression revealed that Gly frequencies did not respond to either elevation or soil type, but were related to summer precipitation (P < 0.01). The correlation between summer precipitation and the frequency of the Gly‐3 allele was r = ?0.92 (P < 0.001). Thus, the patterns of differentiation on microgeographical scales are consistent with greater differentiation on a range‐wide scale.     

Coalescent analyses support multiple mainland-to-island dispersals in the evolution of Malagasy Triaenops bats (Chiroptera: Hipposideridae)

Aim We investigate the directionality of mainland‐to‐island dispersals, focusing on a case study of an African‐Malagasy bat genus, Triaenops (Hipposideridae). Taxa include T. persicus from east Africa and three Triaenops species from Madagascar (T. auritus, T. furculus, and T. rufus). The evolution of this bat family considerably post‐dated the tectonic division of Madagascar from Africa, excluding vicariance as a viable hypothesis. Therefore, we consider three biogeographical scenarios to explain these species' current ranges: (A) a single dispersal from Africa to Madagascar with subsequent speciation of the Malagasy species; (B) multiple, unidirectional dispersals from Africa to Madagascar resulting in multiple, independent Malagasy lineages; or (C) early dispersal of a proto‐species from Africa to Madagascar, with later back‐dispersal of a descendant Malagasy taxon to Africa. Location East Africa, Madagascar, and the Mozambique Channel. Methods We compare the utility of phylogenetic and coalescent methodologies to address the question of directionality in a mainland‐to‐island dispersal event for recently diverged taxa. We also emphasize the application of biologically explicit demographic systems, such as the non‐equilibrium isolation‐with‐migration model. Here, these methods are applied to a four‐species haploid genetic data set, with simulation analyses being applied to validate this approach. Results Coalescent simulations favour scenario B: multiple, unidirectional dispersals from Africa to Madagascar resulting in multiple, independent Malagasy bat lineages. From coalescent dating, we estimate that the genus Triaenops was still a single taxon approximately 2.25 Ma. The most recent Africa to Madagascar dispersal occurred much more recently (c. 660 ka), and led to the formation of the extant Malagasy species, T. rufus. Main conclusions Haploid genetic data from four species of Triaenops are statistically most consistent with multiple, unidirectional dispersals from mainland Africa to Madagascar during the late Pleistocene.     

Evaluating dominance as a component of non-native species invasions

Many studies have quantified plant invasions by determining patterns of non‐native species establishment (i.e. richness and absolute cover). Until recently, dominance has been largely overlooked as a significant component of invasion. Therefore, we re‐examined a 6‐year data set of 323 0.1 ha plots within 18 vegetation types collected in the Grand Staircase‐Escalante National Monument from 1998 to 2003, including dominance (i.e. relative cover) in our analyses. We specifically focused on the non‐native species Bromus tectorum, a notable dominant annual grass in this system. We found that non‐native species establishment and dominance are both occurring in species‐rich, mesic vegetation types. Therefore, non‐native species dominance may result despite many equally abundant native species rather than a dominant few, and competitive exclusion does not seem to be a primary control on either non‐native species establishment or dominance in this study. Unlike patterns observed for non‐native species establishment, relative non‐native species cover could not be predicted by native species richness across vegetation types (R² < 0.001; P = 0.45). However, non‐native species richness was found to be positively correlated with relative non‐native species cover and relative B. tectorum cover (R² = 0.46, P < 0.01; R² = 0.17, P < 0.01). Analyses within vegetation types revealed predominantly positive relationships among these variables for the correlations that were significant. Regression tree analyses across vegetation types that included additional biotic and abiotic variables were a little better at predicting non‐native species dominance (PRE = 0.49) and B. tectorum dominance (PRE = 0.39) than at predicting establishment. Land managers will need to set priorities for control efforts on the more productive, species‐rich vegetation types that appear to be susceptible to both components of invasion.     

Evolutionary history of the Maltese wall lizard Podarcis filfolensis: insights on the ‘Expansion–Contraction’ model of Pleistocene biogeography

The expansion–contraction (EC) model predicts demographic and range contraction of temperate species during Pleistocene glaciations as a consequence of climate‐related habitat changes, and provides a paradigm for explaining the high intraspecific diversity found in refugia in terms of long‐term demographic stability. However, recent evidence has revealed a weak predictive power of this model for terrestrial species in insular and coastal settings. We investigated the Pleistocene EC dynamics and their evolutionary consequences on temperate species using the Maltese archipelago and its endemic lizard Podarcis filfolensis as a model system. The evolutionary and demographic history of P. filfolensis as inferred from mitochondrial and nuclear sequences data does not conform to the EC model predictions, supporting (i) demographic and spatial stability or expansion, rather than contraction, of the northern and southern lineages during the last glacial period; and (ii) a major role for allopatric differentiation primed by sea‐level dynamics, rather than prolonged demographic stability, in the formation of the observed genetic diversity. When combined with evidence from other Mediterranean refugia, this study shows how the incorporation of Pleistocene sea‐level variations in the EC model accounts for a reverse demographic and range response of insular and coastal temperate biotas relative to continental ones. Furthermore, this cross‐archipelago pattern in which allopatric diversity is formed and shaped by EC cycles resembles that seen between isolated populations within mainland refugia and suggests that the EC model, originally developed to explain population fluctuations into and out‐of refugia, may be appropriate for describing the demographic and evolutionary dynamics driving the high genetic diversity observed in these areas.     

Patterns of speciation in two sibling species of Graomys (Rodentia,Cricetidae) based on mtDNA sequences

To increase our understanding of the speciation process occurred in the sibling species Graomys griseoflavus and Graomys centralis, a phylogeographic study was conducted based on sequences of a hypervariable segment of the mtDNA D‐loop region. The resulting haplotype phylogenetic network showed two well‐defined clusters, one for each species. The clusters were connected by two haplotypes from localities that are almost 300 km apart, one situated in the Monte eco‐region and the other, in the Chaco. This result is in agreement with a previous hypothesis about the geographical context in which the cladogenetic process occurred. A divergence time of 0.15–0.28 million years was estimated, which is consistent with a process of recent speciation. An amova test confirmed that at present gene flow between species does not exist. The mismatch distribution analyses suggest that the geographical and demographic expansion undergone by the species is related to the climatic events that occurred in the region during the Quaternary.