Dispersal across habitat boundaries: uncovering the demographic fates of populations in unsuitable habitat

Patchy landscapes are characterized by abrupt transitions among distinct habitat types, forcing species to cross habitat boundaries in order to spread. Since seed dispersal is a probabilistic process, with a kernel that decays with distance, most individuals will fail to reach new, suitable habitat. Although failed dispersers are presumed dead in population models, their demographic fates may not be so simple. If transient survival is possible within unsuitable habitat, then through time, individuals may be able to reach distant, suitable habitat, forming new populations and buffering species from extinction. In a fragmented Californian grassland, we explored the fates of individuals that crossed habitat boundaries, and if those fates differed among specialists dispersing from two habitat types: serpentine habitat patches and the invaded non-serpentine matrix. We surveyed the diversity of seedbank and adult life stages along transects that crossed boundaries between patches and the matrix. First, we considered how patch specialists might transiently survive in the matrix via seed dormancy or stepping-stone populations. Second, we investigated the dispersal of an invasive matrix specialist (Avena fatua) into patches, to assess if sink populations existed across the habitat boundary. We found that dormancy maintained populations of patch specialists deep into the matrix, as abundances of seedbanks and of adult plant communities differed with distance into the matrix. We found evidence that these dormant seeds disperse secondarily with vectors of material flows in the landscape, suggesting that they could eventually reach suitable patches even if they first land in the matrix. We found that A. fatua were largely absent deep in patches, where reproductive outputs plummeted and there was no evidence of a dormant seedbank. Our results not only reveal the demographic fates of individuals that land in unsuitable habitat, but that their ecological consequences differ depending on the direction by which the boundary is crossed (patch → matrix ≠ matrix → patch). Dormancy is often understood as a mechanism for persisting in face of temporal variability, but it may serve as a means of traversing unsuitable habitat in patchy systems, warranting its consideration in estimates of habitat connectivity.

Fishing the line depends on reserve benefits, individual losing at boundary and movement preference

Whether fishing around the marine reserve edge can enhance harvested yields is an important issue in fisheries management. To solve the conundrum is difficult because of the lack of a matched boundary condition. Here, we derive a new boundary condition by considering individual losing at habitat boundaries. With the suitable boundary condition, our results suggest that individuals with high growth rate inside but low growth rate outside the reserve and high movement preference to a large marine reserve boundary can enhance yields benefits from fishing around the marine reserve edge. The findings provide theoretical cautions for fishing near some new reserves in which population growth rate might be low. Moreover, our boundary condition is general enough for the universal phenomenon of losing individual at habitat boundaries such as being applied into classic theories in refuge design to explain some previous counter-intuitive phenomena more reasonably.

GEOGRAPHICAL ANALYSIS OF SIZE AND PATTERN OF VILLAGES IN RAMPUR DISTRICT

Habitat geography is the new sprout branch of human geography. Both rural domicile and urban domicile are the two main strands of geography. Habitat geography studies the effect of physical and cultural considerations on man-made habitats, just as human geography describes the environment and human interactions. Human occupancy is the focal center within and around which man builds his culture. Human occupancy refers to all the natural elements and man-made structures that the process of habitat establishes, habitat boundaries that separate them from each other, spatial relationships that link them to both adjacent and remote areas, and The institute, which has been set up to maintain its social and cultural, economic, political and other importance. अधिवास भूगोल मानव भूगोल की नवीन अंकुरित शाखा है। ग्रामीण अधिवास और नगरीय अधिवास दोनों ही अधिवास भूगोल के दो प्रमुख तन्तु है। अधिवास भूगोल मानव द्वारा निर्मित आवासों पर भौतिक तथा सांस्कृतिक बातों के प्रभाव का अध्ययन करता है, ठीक उसी भाॅंति जिस प्रकार मानव भूगोल वातावरण तथा मानव के पारस्परिक सम्बन्धों का विष्लेशण करता है। मानव अधिवास वह नाभीय केन्द्र है जिनके भीतर व जिसके चारों ओर मानव अपनी संस्कृति का निर्माण करता है। मानव अधिवास उन सभी प्राकृतिक तत्वों और मानव निर्मित संरचनाओं की ओर संकेत करता है जो बसाव स्थापन की प्रक्रिया आवासों का स्थापन, मानवीय सीमाएँ जो उनको एक-दूसरे से अलग करती है, स्थानिक सम्बन्ध जो उसको समीपवर्ती तथा दूरस्थ दोनों ही क्षेत्रों से जोड़ते है तथा वह संस्थान सामाजिक सांस्कृतिक, आर्थिक, राजनीतिक तथा अन्य जिनका स्थापन उसे संचालित व प्रधानता बनाये रखने के लिए किया गया है।

Permeability of habitat edges for Ringlet butterflies (Lepidoptera, Nymphalidae, Erebia Dalman 1816) in an alpine landscape

We tracked the movements of adult Ringlet butterflies (Lepidoptera, Nymphalidae, Erebia Dalman, 1816) in high-elevation (> 1800 meters a.s.l.) grasslands in the Austrian Alps in order to test if an anthropogenic boundary (= an asphalt road) had a stronger effect on butterfly movement than natural habitat boundaries (trees, scree, or dwarf shrubs surrounding grassland sites). 373 individuals (136 females, 237 males) belonging to 11 Erebia species were observed in one flight season (July–August 2013) while approaching or crossing habitat edges. Erebia pandrose (Borkhausen, 1788) was the most abundant species with 239 observations. All species studied were reluctant to cross habitat boundaries, but permeability was further strongly affected by the border type. Additional variables influencing movement probability were species identity and the time of the day. In E. pandrose, for which we had sufficient observations to analyse this, individuals were more likely to cross a boundary in the morning and in the late afternoon than at midday. Erebia euryale (Esper, 1805) and E. nivalis Lorković & de Lesse, 1954 were more likely to leave a habitat patch than their studied congeners. The key result of our study is that the paved road had the lowest permeability among all edge types (0.1 likelihood of crossing when approaching the edge). A road cutting across a conservation area (viz. a national park) thus hinders inter-patch exchange among Ringlet butterflies in the alpine zone, even though theoretically they ought to be able to fly across.

Metabolic insight into bacterial community assembly across ecosystem boundaries

ABSTRACTThe movement of organisms across habitat boundaries has important consequences for populations, communities, and ecosystems. However, because most species are not well adapted to all habitat types, dispersal into suboptimal habitats could induce physiological changes associated with persistence strategies that influence community assembly. For example, high rates of cross-boundary dispersal are thought to maintain sink populations of terrestrial bacteria in aquatic habitats, but these bacteria may also persist by lowering their metabolic activity, introducing metabolic heterogeneity that buffers the population against niche selection. To differentiate between these assembly processes, we analyzed bacterial composition along a hydrological flow path from terrestrial soils through an aquatic reservoir by sequencing the active and total (active + inactive) portions of the community. When metabolic heterogeneity was ignored, our data were consistent with views that cross-boundary dispersal is important for structuring aquatic bacterial communities. In contrast, we found evidence for strong niche selection when metabolic heterogeneity was explicitly considered, suggesting that, relative to persistence strategies, dispersal may have a weaker effect on aquatic community assembly than previously thought. By accounting for metabolic heterogeneity in complex communities, our findings clarify the roles of local- and regional-scale assembly processes in terrestrial-aquatic meta-ecosystems.

Investigating Aquatic Insect Emergence: A Demonstration of the 5E Learning Cycle

Traditionally, exploration of ecosystems in the context of undergraduate education has been restricted to connections within conventionally defined habitats (i.e., within a stream, within a forest). Further, instruction regarding the aquatic-terrestrial interface has emphasized directional inputs from land to water. However, a relatively new body of research has characterized reciprocal interactions and draws attention to fluxes from water to land, including the emergence of aquatic insects that serve as prey for terrestrial predators. We present a guide to an inquiry-based lesson for undergraduate biology that explores interactions and connections across aquatic and terrestrial habitat boundaries. The focus is on cross-habitat linkages within ecosystems, specifically addressing the question, What is the role of insect emergence in connecting the web of life linking aquatic and terrestrial habitats and organisms? Students (1) engage with a documentary film, (2) explore insect emergence and make observations of riparian insectivores, (3) explain the collected data, (4) elaborate on alternative study designs and a measure of ecosystem health, and (5) evaluate their new understanding. This lesson addresses core concepts and competencies for undergraduate biology education, as identified in the Vision and Change report.