Habitat selection of nesting and fledgling salt marsh songbirds in northeast Florida

Understanding habitat selection by breeding birds and their newly fledged young can be an essential aspect of the conservation of vulnerable species. During 2015–2017, we examined nest site selection of Worthington's marsh wren (Cistothorus palustris griseus) and MacGillivray's seaside sparrow (Ammospiza maritima macgillivraii), and fledgling habitat use by Worthington's marsh wren, 2 imperiled species in northeast Florida, USA. We compared vegetation at unused points to vegetation at nests of both subspecies and at locations used by radio-tagged marsh wren fledglings. Vegetation was taller and stem counts were greater at nest sites compared to unused points. Worthington's marsh wrens also used nest sites with a greater proportion of tall-form smooth cordgrass (Spartina alterniflora) than was observed at unused points. Worthington's marsh wren fledglings also used locations with taller, denser vegetation, but vegetation use changed with fledgling age and tidal stage; older fledglings more frequently used areas with short-form smooth cordgrass and bare ground (and more so during low tides). In contrast, so few nests and nestlings were in black needlerush (Juncus roemerianus) that we could not consider it in our analysis despite its prevalence within our study sites. Our results indicate that tall, dense cordgrass is an important habitat component for these subspecies during the nesting and fledgling life stages in southeastern Atlantic salt marshes.     

The effects of fire on the frillneck lizard (Chlamydosaurus kingii) in northern Australia

Abstract A population of frillneck lizards, Chlamydosaurus kingii, was monitored by radio telemetry and mark-recapture techniques between April 1991 and April 1994, as part of a landscape-scale fire experiment, in Kakadu National Park, Northern Territory. The study aimed to investigate both the short- and longer-term effects of fire on a lizard species in a tropical savanna where fires are frequent and often annual. Frillneck lizards are able to survive fires that occur in the first few months of the dry season by remaining perched in trees. A high level of mortality (29%) occurred during late dry-season fires, along with changes in their behavioural response to fire: sheltering in either larger trees or hollow termite mounds. Food is more accessible after fires due to the removal of ground vegetation. This is reflected in greater volume and diversity of prey in stomach contents after fires. This increase is more pronounced after late dry-season fires, possibly due to increased accessibility of prey caused by more complete vegetation removal. Frillneck lizards show an overall preference for trees with a dense canopy cover located in an area with a low density of grass. Fire has an effect on this relationship. Frillneck lizards in habitat unburnt for a number of years tend to perch in trees with a smaller canopy, whereas lizards in annually burnt habitat perch in trees with a dense canopy. Volume and composition of lizard stomach contents was broadly similar among fire treatments over a 2 year period, although termites were more predominant in stomach contents of lizards in unburnt habitat. Wet-season body condition is lower in lizards from unburnt habitat, although the reason for this is unclear. These results demonstrate the importance of different fire intensities and regimes on the ecology of a lizard species in a tropical savanna.     

Fire‐mediated niche‐separation between two sympatric small mammal species

Fire is a key ecological process influencing the population dynamics of small mammals. Whilst shifting competitive advantage amongst small mammal species following a single fire event is well‐documented, there has been little investigation of the potential influence of fire frequency on small mammal interspecific interactions. In this study, we investigated the effect of fire frequency on the abundance of two small dasyurid mammals, Antechinus stuartii and A. flavipes, which occur sympatrically in some parts of their range. The two antechinus species are known to have different habitat preferences, so it is possible that fire regimes may promote their coexistence in areas of sympatry by altering vegetation structure. To investigate this possibility, we estimated the abundance of both species using replicate sites which differed in the number of times burnt (1–4) during the last four decades, but with identical time‐since‐fire. Proportionally, we captured greater numbers of A. stuartii in less frequently burnt sites and greater numbers of A. flavipes in more‐frequently burnt sites. Hence, fire may mediate niche‐separation between these two species. To clarify further this pattern of response to fire frequency, we investigated which structural habitat variables differed between fire frequencies, and compared antechinus abundances with structural vegetation characteristics. We found a trend for lower ground cover density under higher fire frequencies. This offers one potential explanation of the patterns of abundance that we observed. Our study provided insights into the complexities of small mammal responses to fire, and strongly suggests that fire could mediate competitive interactions between species.     

Does the rare Banksia goodii have inferior vegetative,reproductive or ecological attributes compared with its widespread co-occurring relative B. gardneri?

Banksia goodii (rare) and B. gardneri var. gardneri (widespread) are closely related rhizomatous evergreen subshrubs of south western Australian scrub-heath and woodland. B. goodii is restricted to sixteen populations, most of which are remnants on roadsides due to landscape fragmentation from agricultural activities. Bioclimatic profiles indicate that B. gardneri spans a wider range of climates than B. goodii. However, their post-fire survival and resprouting vigour, rates of seedling growth and soil penetration and susceptibility to seedling predators are similar. Both have the potential for geographic range extension, especially B. goodi. Seedlings of both species survived for at least 3 years at sites with 2 (but not 3) months shorter and 1 month longer growing seasons than experienced by natural B. goodii populations. Seedling establishment did not occur in the absence of fire and was low (1.3% of released intact seeds for B. goodii) even following en masse release of seeds after fire. Sowing of intact seeds, especially in cleared areas and with protection from herbivores, increased this to 35%. Fire survival among adults of both species was 100% following two fires. B. goodii, which roots along its rhizomes, produces ramets, while B. gardneri, with a lignotuber instead, does not. Seed production, pre-dispersal granivory and canopy seed storage are low but similar for both species, although B. gardneri has a superior level of germination. The biology of B. gardneri thus provides few insights as to why B. goodii is rare. There were no differences in topo-edaphic attributes, community structure, shading or litter cover between localized sites where either species occurred alone or together. Differences in present or prehistoric fire regimes, clearing (habitat fragmentation), susceptibility to generalist fungal pathogens, or impacts of alien invasives, cannot explain the distribution of B. goodii relative to B. gardneri. The rarity of B. goodii may be a result of its recent origin, habitat specialization (dense woodland), and the impacts of habitat fragmentation within its current range, rather than inferior vegetative, reproductive and/or ecological attributes.     

Predicting the post-fire establishment and persistence of an invasive tree species across a complex landscape

The reintroduction of pre-European fire regimes has allowed the entry of many invasive plant species into fire-dependant ecosystems of North America. However, the environmental factors that favor the post-fire establishment of these species across complex landscapes are not well understood and the initial establishment of invasive species does not necessarily result in long-term persistence. To evaluate the post-fire establishment and persistence of disturbance-dependent invasive plants, we studied the invasion of Paulownia tomentosa (princess tree, an early-successional species introduced from Asia) across three burns in the southern Appalachian Mountains. Based upon classification tree analysis, the presence/absence of P. tomentosa 2 years after burning was most strongly related to the cover of residual vegetation, topographic shading, and moisture availability. Spatial application of classification tree models to repeated survey data showed that P. tomentosa established across a wide range of microsites 2 years after burning. However, predicted habitat for P. tomentosa decreased by 63% 4 years after fire and by 73% 6 years after fire. Following its initial widespread establishment, P. tomentosa only persisted on xeric and exposed topographic positions that experienced high intensity burning. However, the sites where it persisted include rare community types that contain two endangered plant species that depend upon fire for successful reproduction. The control of P. tomentosa on these ecologically important sites may require special attention from land managers.     

The effect of heat and smoke on the soil seed banks of heathlands on permanent freshwater swamps

In South Australia, Swamps of the Fleurieu Peninsula are critically endangered due to past vegetation clearance and changes in hydrology, but still contain a high diversity of threatened plant species. This vegetation community provides habitat for 82 threatened ground-stratum plant species, including the nationally critically endangered subshrub Hibbertia tenuis which is endemic to these swamps. With infrequent burning, native ferns and taller shrubs outcompete these species. We conducted glasshouse trials to determine the potential of fire to regenerate threatened and other swamp plant species. Soil samples from eight swamps were used in germination trials with half of each sample treated with heat plus smoke, and half left untreated. Samples were spread onto trays (n = 188), and seedling emergence was recorded for twelve months. Emergence was dominated by native species (2649 seedlings m⁻²) compared to exotics (675 seedlings m⁻²). In total, 48 native and 25 introduced species germinated, with 21% of germinated native species absent from the above-ground vegetation. The dominant native fern Gleichenia microphylla did not emerge from any soil samples, indicating that recovery likely lags behind that of ground-strata species, giving them time to establish and set seed before being outcompeted. Thirty-four rare or threatened species germinated, including five species absent from above-ground vegetation. Of all native species that emerged, only five were confined to heat plus smoke treatments, suggesting most species will regenerate without fire if overstorey competition is reduced. However, seedling emergence of native shrubs/subshrubs more than doubled with the fire treatment. Of particular importance, H. tenuis showed an 18-fold increase in germination when treated with heat plus smoke. This study supports the utility of ecological burns as a management tool to regenerate threatened plant species in long-undisturbed peaty heathlands on permanent swamps.     

Effects of fire regime on plant species richness and composition differ among forest,woodland and heath vegetation

Question

Do the effects of fire regimes on plant species richness and composition differ among floristically similar vegetation types?

Location

Booderee National Park, south‐eastern Australia.

Methods

We completed floristic surveys of 87 sites in Sydney Coastal dry sclerophyll vegetation, where fire history records have been maintained for over 55 years. We tested for associations between different aspects of the recent fire history and plant species richness and composition, and whether these relationships were consistent among structurally defined forest, woodland and heath vegetation types.

Results

The relationship between fire regime variables and plant species richness and composition differed among vegetation types, despite the three vegetation types having similar species pools. Fire frequency was positively related to species richness in woodland, negatively related to species richness in heath, and unrelated to species richness in forest. These different relationships were explained by differences in the associations between fire history and species traits among vegetation types. The negative relationship between fire frequency and species richness in heath vegetation was underpinned by reduced occurrence of resprouting species at high fire frequency sites (more than four fires in 55 years). However, in forest and woodland vegetation, resprouting species were not negatively associated with fire frequency.

Conclusions

We hypothesize that differing relationships among vegetation types were underpinned by differences in fire behaviour, and/or biotic and abiotic conditions, leading to differences in plant species mortality and post‐fire recovery among vegetation types. Our findings suggest that even when there is a high proportion of shared species between vegetation types, fires can have very different effects on vegetation communities, depending on the structural vegetation type. Both research and management of fire regimes may therefore benefit from considering vegetation types as separate management units.     

The habitat and conduit functions of roads in the spread of three invasive plant species

Nonnative plant species commonly occur along roadsides, and populations are often assumed to invade by spread along the road axis. To distinguish between the function of roadsides as movement corridors and as habitat, nonnative plant species were surveyed along roads in deciduous forest sites in southeastern Ohio, USA. The importance of road proximity was tested by comparing nonnative species abundance in 100 m transects along roads with transects in undisturbed forest. Nonnative species were most abundant and most frequently observed in roadside sites in valleys. Three common species were chosen for closer scrutiny. In a seed sowing experiment roads and open sites proved to be better locations for the germination and growth of Microstegium vimineum than non-roadside and closed-canopy sites. Tussilago farfara and Rosa multiflora occurred in a small number of disjunct patches suggesting infrequent arrival in the sampled transects. Both species were strongly clustered at scales consistent with diffusive spread by vegetative growth and short-range seed dispersal. Comparisons of distributions parallel and perpendicular to roads showed no evidence for enhanced dispersal along the road axis. Microstegium distributions were correlated with local light availability implying site saturation. Microstegium micro-distributions suggested that spread along the road axis was facilitated by movement of dormant seeds in road maintenance. Thus, roadsides appear to function as both habitat and a conduit for population expansion, with the rate of spread dependent on the life history of the individual species. These results suggest a hierarchical process of regional invasion, with different dispersal mechanisms functioning at different spatial scales.     

Forest edges and fire ants alter the seed shadow of an ant-dispersed plant

Exotic species invade fragmented, edge-rich habitats readily, yet the distinct impacts of habitat edges and invaders on native biota are rarely distinguished. Both appear detrimental to ant-dispersed plants such as bloodroot, Sanguinaria canadensis. Working in northeastern Georgia (USA), an area characterized by a rich ant-dispersed flora, fragmented forests, and invasions by the red imported fire ant, Solenopsis invicta , I monitored the interactions between ants and S. canadensis seeds in uninvaded forest interiors, uninvaded forest edges, invaded forest interiors, and invaded forest edges. I observed 95% of the seed dispersal events that occurred within the 60-min observation intervals. Seed collection rates were similar among all four (habitat × invasion) groups. The presence of invasive ants had a strong effect on seed dispersal distance: S. invicta collected most seeds in invaded sites, but was a poorer disperser than four of five native ant taxa. Habitat type (interior versus edge) had no effect on seed dispersal distance, but it had a strong effect on seed dispersal direction. Dispersal towards the edge was disproportionately rare in uninvaded forest edges, and ants in those habitats moved the average dispersed seed approximately 70 cm away from that edge. Dispersal direction was also skewed away from the edge in uninvaded forest interiors and invaded forest edges, albeit non-significantly. This biased dispersal may help explain the rarity of myrmecochorous plants in younger forests and edges, and their poor ability to disperse between fragments. This is the first demonstration that forest edges and S. invicta invasion influence seed dispersal destination and distance, respectively. These forces act independently.     

Lizard responses to wildfire in arid interior Australia: Long‐term experimental data and commonalities with other studies

Life in terrestrial Australian ecosystems has evolved over the past 10 million years to thrive in habitats kept in a dynamic state through fire succession cycles. Previous studies support the notion that wildfires promote species diversity in plant and animal communities by creating a heterogeneous mix of habitats, each habitat more suitable for particular subsets of species. We document population and community responses to fire in a species‐rich lizard assemblage in the Great Victoria Desert of Western Australia. Lizards were censused by pit trapping at a long‐unburned flat spinifex site in the Great Victoria Desert in Austral springs of 1992 and 1995. A controlled burn was undertaken in mid‐October of 1995, and lizards were censused thereafter in late 1995 and early 1996, and then again in the Austral springs of 1998, 2003 and 2008. Forty‐six species of lizards (2872 individuals) were collected and their stomach contents analysed over the course of a 16‐year fire succession cycle at this single study site. Most strikingly, relative abundances of two species of agamids varied inversely, responding oppositely to habitat clearing effects of fire. The military dragon Ctenophorus isolepis reached higher abundances when vegetation was dense, and decreased in abundance in open vegetation following fire. The netted dragon Ctenophorus nuchalis was rare when vegetation coverage was high but increased rapidly after fire. Abundances of five species of Ctenotus skinks, C. ariadnae, C. calurus, C. hanloni, C. pantherinus and C. piankai, tracked those of C. isolepis. Abundance of a termite‐specialized nocturnal gecko, Rhynchoedura ornata, increased in abundance following fire. Lizard diets changed during the course of the fire succession cycle, returning to near pre‐burn conditions after 16 years. In addition to short‐term fire succession cycles that contribute to structuring local communities, changes in long‐term rainfall also impact desert food webs and regional biotas.     

Disturbance processes and spatial patterns of two emergent conifers in New Caledonia

Abstract Araucaria laubenfelsii Corbasson and Araucaria montana Brongn et Gris are emergent conifers in maquis and forest communities which are subjected to a combination of fire and cyclonic disturbances. Both species are able to survive fire once stems reach a critical size, but most seedlings and saplings are killed. Both species were found to be clumped at most spatial scales for both saplings and trees in maquis, probably resulting from a combination of patchy fire and a limited ability to disperse seeds. Comparisons of burned and unburned A. montana sites suggest that clumping increases only slightly after fire. The degree of clumping in the A. laubenfelsii sites, suggested that fire disturbances may occur relatively frequently in the region. Cyclonic disturbances are infrequent but may result in blow‐down of large individuals within both maquis and forest. All of the individuals blown‐down during the study had been previously fire‐scarred. Around tree blow‐downs, seedling and sapling densities can be high. This likely reflects both the low dispersability of Araucaria seeds and enhanced moisture from the shading of the adult, when it was alive. Disturbance by fire and wind play an important role in the regeneration dynamics and spatial pattern of these species in maquis in New Caledonia.     

Impact of native vegetation cover near crops on the occurrence and molecular diversity of fire ants

Solenopsis invicta and Solenopsis saevissima are the most common fire ants in Brazil. Environmental disturbances favour the colony dispersal of both species, particularly those with an anthropogenic origin. However, the frequencies of the species can vary according to the amount of anthropogenic disturbances. Crops near native vegetation fragments is a common landscape in the Brazilian Atlantic Forest. Here, we analyse if there is influence of native vegetation cover on the occurrence of these fire ants and their molecular diversity in crops. Our hypothesis is that these species are antagonistic in terms of occurrence and molecular diversity when compared in the same habitat. We selected crops near fragments with around 50% of native vegetation cover, a percentage informative enough to detect biological responses from insects belonging to a same order. Nests were collected and the species were identified using external morphology, and mtDNA COI sequences. We reject our hypothesis, which suggest that the species colonize the vegetation patches around crops in a similar way. Solenopsis invicta is not limited by vegetation cover, and has a high haplotype diversity when compared to S. saevissima, particularly when the vegetation cover is greater than 50%. Additionally, the vegetation cover seems to not have influence in the total number of haplotypes, but the species have haplotypes that are exclusive to each landscape. Our findings suggest that S. invicta is expanding to native vegetation areas that it has not occupied before, as S. saevissima was dominant there.     

The Arrhenatheretum on set-aside at Aldroughty,Elgin

Summary

The Arrhenatheretum on set-aside in two fields at Aldroughty Farm, Elgin, is described. This vegetation is noteworthy because some of the attractive grassland and wetland species in it are very rare on Scottish set-aside. The species involved (e.g. Carex flacca, Dactylorhiza purpurella, Rhinanthus minor) are generally entirely absent from lowland farmed landscapes, but populations do occur in areas of semi-natural habitat at Aldroughty. It is concluded that, as far as most long-term set-aside is concerned, vegetation of greater conservation value does not develop thereon owing to non-availability of the necessary seeds.     

Life history influences how fire affects genetic diversity in two lizard species

‘Fire mosaics’ are often maintained in landscapes to promote successional diversity in vegetation with little understanding of how this will affect ecological processes in animal populations such as dispersal, social organization and re‐establishment. To investigate these processes, we conducted a replicated, spatiotemporal landscape genetics study of two Australian woodland lizard species [Amphibolurus norrisi (Agamidae) and Ctenotus atlas (Scincidae)]. Agamids have a more complex social and territory structure than skinks, so fire might have a greater impact on their population structure and thus genetic diversity. Genetic diversity increased with time since fire in C. atlas and decreased with time since fire in A. norrisi. For C. atlas, this might reflect its increasing population size after fire, but we could not detect increased gene flow that would reduce the loss of genetic diversity through genetic drift. Using landscape resistance analyses, we found no evidence that postfire habitat succession or topography affected gene flow in either species and we were unable to distinguish between survival and immigration as modes of postfire re‐establishment. In A. norrisi, we detected female‐biased dispersal, likely reflecting its territorial social structure and polygynous mating system. The increased genetic diversity in A. norrisi in recently burnt habitat might reflect a temporary disruption of its territoriality and increased male dispersal, a hypothesis that was supported with a simulation experiment. Our results suggest that the effects of disturbance on genetic diversity will be stronger for species with territorial social organization.     

Environmental correlates of growth traits of the stoloniferous plant Potentilla palustris

Growth form is one of the important life history traits ultimately influencing plant fitness. Potentilla palustris is a stoloniferous plant growing in a range of habitats from densely vegetated wet meadows to acidic transitional fens, and its growth form varies according to habitat. In a four year multi-site comparative study, we investigated which biotic and abiotic characteristics influence most its growth traits. Vegetation composition and physiognomy, as well as numerous abiotic environmental variables, were recorded at 32 study sites located on an altitudinal gradient. Growth traits of P. palustris were best explained by the surrounding vegetation physiognomy and not by abiotic conditions, although the latter obviously represents the factors indirectly influencing its growth. Stolon length traits and branching were positively correlated with vegetation density and height, and negatively with altitude. Plants flowered more in taller vegetation, and leaf area was greater in wetter sites with lower vegetation cover. Potentilla palustris appeared to be well adapted to transitional fens, but its vegetative growth was fastest in wet meadows and alluvial habitats on highly organic humid soils. It produced more branches and larger leaves in alluvial habitats with open water, while it had enhanced generative reproduction in wet meadows. Species composition was less important than vegetation physiognomy. In less favorable habitat types, P. palustris prefers an escape strategy of linear growth. Internode length exhibited pronounced plasticity, increasing particularly in tall dense vegetation of lower altitude, whereas internode number remained fairly constant over various habitats. It is evident that both plastic low cost growth traits (internode elongation), and constant high cost traits (internode number) contribute to the P. palustris escape strategy under tall dense vegetation. Phenotypic plasticity enhances the potential of P. palustris to grow in a wide range of habitats and so increases plant fitness on regional scale.     

How high is your hummock? The importance of Triodia height as a habitat predictor for an endangered marsupial in a fire‐prone environment

Fire and seral vegetation succession are known to influence the distribution and abundance of a wide range of arid and semi‐arid mammal species. In Triodia hummock grasslands, the gradual increase in Triodia cover after fire is a significant factor influencing mammal distribution and abundance. However, the height of fire‐adapted hummock grass species is often ignored during habitat preference studies despite the fact that taller hummocks are likely to have improved insulation properties and greater protection from predators. We tested the relative importance of a range of Triodia habitat characteristics in determining the distribution and abundance of a fire‐adapted mammal inhabiting Triodia mallee dune fields in semi‐arid Australia. We sampled 77 sites and collected information on habitat attributes including Triodia cover, height and time since fire. The 90th percentile Triodia height (>400 mm) was the most reliable predictor of sandhill dunnart abundance, and breeding, inferred through the presence of subadults. The presence of adult sandhill dunnarts was best explained by Triodia cover, increasing when cover exceeded 25%. We suggest that while Triodia cover may be an important variable for predicting the presence of adult sandhill dunnarts, the height of Triodia is important for breeding, when tall Triodia are possibly sought for nesting sites. These Triodia height and cover requirements were not recorded at sites until at least 10 years post fire but the relationship between fire and Triodia cover and height was inconsistent; after 20 years Triodia cover declined with increasing fire age while the 90th percentile Triodia height remained relatively constant. This incongruence may explain why the presence of sandhill dunnarts appears more constrained by a minimum rather than maximum time since fire and could help explain patterns of post‐fire distribution in other arid zone mammals. Importantly, the 90th percentile Triodia height highlighted the possible significance of scattered, tall Triodia hummocks for arid zone fossorial mammals.     

Influence of grazing and fire on breeding birds and perennial plants in Cyprus scrub and forest systems

Grazing and browsing by sheep and goats has been an important anthropogenic influence on ecosystems in the Mediterranean region for centuries. This influence has changed significantly in recent decades, with a general shift from range grazing to the penning of animals. The intermediate disturbance hypothesis (IDH) proposes that perturbation - including anthropogenic disturbance - is the norm for Mediterranean ecosystems, and that higher species diversity is found under conditions of continuous, moderate disturbance. Here we test the IDH as it relates to grazing of scrub and open forest habitats in Cyprus, while also testing for the effects of fire. We carried out surveys of breeding birds and vegetation at 48 study sites in scrub and open woodland across Cyprus. We estimated relative grazing pressure (past and present) and fire history at these sites, and tested for associations between these factors, breeding bird species richness and perennial vegetation diversity. We found moderate current grazing reduces density of lower and middle level scrub, and a higher level of diversity of perennial vegetation at moderately over intensively grazed sites. We found that moderate historical grazing pressure had a positive influence on richness of breeding bird species in lower scrub habitat such as phrygana, but that this effect was weaker the taller and denser the habitat. By contrast, current grazing pressure had a negative effect on species richness in lower scrub, but species richness in grazed habitats was higher in denser, taller scrub habitat such as garrigue and maquis. Our study suggests grazing plays an important role in maintaining habitat heterogeneity but the impact on avian species richness depends on the density and height of the vegetation.     

Ant-mediated expansion of an obligate seeder species during the first years after fire

Most obligate seeder species build up a soil seed bank that is associated with massive seed germination in the year immediately after a fire. These species are also shade‐intolerant and disappear when vegetation cover closes, creating unsuitable conditions for seedling recruitment. The only way for these plants to expand their populations is when habitats suitable for seedling recruitment arise (i.e. in years immediately after a fire). However, short primary seed dispersal of obligate seeders does not allow these plants to colonise the suitable habitats, and these habitats can only be colonised by secondary seed dispersion. We hypothesised that Fumana ericoides, an obligate‐seeding small shrub, not only establishes abundantly in the first year after fire, but also expands its local range in the following years due to secondary dispersal by ants while suitable habitats are still available. We tested this hypothesis using experimental studies and a simulation model of potential population expansion in a recently burned area. Results showed that F. ericoides not only established prolifically in the year immediately after fire, but was also able to recruit new individuals and expand its population in the years following the fire, despite a low germination rate and short primary seed dispersal. Ant‐mediated seed dispersal and availability of suitable habitats were key factors in this phenomenon: ants redistributed seeds in suitable habitats while they were available, which accelerated the expansion of F. ericoides because new plants established far away from the core population.     

Landscape genetics of an early successional specialist in a disturbance‐prone environment

Species that specialize in disturbed habitats may have considerably different dispersal strategies than those adapted to more stable environments. However, little is known of the dispersal patterns and population structure of such species. This information is important for conservation because many postfire specialists are at risk from anthropogenic changes to natural disturbance regimes. We used microsatellite markers to assess the effect of landscape variation and recent disturbance history on dispersal by a small mammal species that occupies the early seral stage of vegetation regeneration in burnt environments. We predicted that a postfire specialist would be able to disperse over multiple habitat types (generalist) and not exhibit sex‐biased dispersal, as such strategies should enable effective colonization of spatially and temporally variable habitat. We found significant differentiation between sites that fitted an isolation‐by‐distance pattern and spatial autocorrelation of multilocus genotypes to a distance of 2–3 km. There was no consistent genetic evidence for sex‐biased dispersal. We tested the influence of different habitat‐ and fire‐specific landscape resistance scenarios on genetic distance between individuals and found a significant effect of fire. Our genetic data supported recently burned vegetation having greater conductance for gene flow than unburnt habitat, but variation in habitat quality between vegetation types and occupied patches had no effect on gene flow. Postfire specialists must evolve an effective dispersal ability to move over distances that would ensure access to early successional stage vegetation. Natural disturbance and natural heterogeneity may therefore not influence population genetic structure as negatively as expected.     

Influence of fine‐scale habitat requirements and riparian degradation on the distribution of the purple‐crowned fairy‐wren (Malurus coronatus coronatus) in northern Australia

Species distributions are influenced by variation in environmental conditions across many scales. Knowledge of fine‐scale habitat requirements is important for predicting species occurrence and identifying suitable habitat for target species. Here we investigate the perplexing distribution of a riparian habitat specialist, the western subspecies of the purple‐crowned fairy‐wren (Malurus coronatus coronatus), in relation to fine‐scale habitat associations and patterns of riparian degradation. Surveys of vegetation attributes, river structure and disturbance indicators that are likely to be causal determinants of the species occurrence were undertaken at 635 sites across 14 catchments. Generalized Linear Mixed Modelling demonstrated that the probability of purple‐crowned fairy‐wren occurrence increased with Pandanus aquaticus crown cover, shrub density and height of emergent trees, while riparian structure and signs of cattle were indirect predictors of occurrence. As our study area predominantly contained Pandanus type habitat, we failed to identify river grass as an important component of habitat. Predictions from a cross‐validated model of purple‐crowned fairy‐wren occurrence suggested distribution is constrained by three factors: (i) low quality of local habitat within catchments where the species occurs; (ii) broad‐scale reduction in habitat quality that has resulted in extinction of the species from parts of its range; and (iii) unmeasured variables that limit the exploitation of suitable habitat. The reliance of the species on dense shrubby understorey suggests conservation efforts should aim to maintain the complexity of understorey structure by managing fire and grazing intensity. Efforts to halt the continuing decline of riparian condition and maintain connectivity between areas of quality habitat will help to ensure persistence of riparian habitat specialists in northern Australia.