Temporally robust spatial structure in ecosystems explained by local biodiversity regulation

The distribution in species' site occupancy is a fundamental pattern in spatial ecology. Despite decades of research, the mechanisms responsible for the shape of the distribution remain incompletely understood. Here, we simultaneously examining both spatial and temporal patterns of site occupancy in communities of macroinverterbrates, macrophytes and diatoms. We show that a simple patch dynamics model explains both the spatial structure and temporal dynamics in English rivers. The key mechanism responsible for the emergent spatial structure in the model are intrinsic regulation of biodiversity at the local scale which, when combined with inter-site dispersal and regional-scale invasion, drives local colonisation and extinction. Our analysis supports the notion that metacommunities exist in a kind of dynamic steady state arising from local ecological constraints and that this intrinsic regulation can drives the emergence of a wide variety of macroecological patterns.

Patch dynamics in the Javan Hawk-Eagle (Nisaetus bartelsi) habitat of East Java

Javan Hawk-Eagle (JHE, Nisaetus bartelsi) is an endemic species in Java Island and an important biological indicator of ecosystem health. The government has issued regulations to protect this species and increase the population by 10% from 2015 until 2019. East Java has the largest JHE potential habitat in Java Island based on a previous study using satellite images of 2002. Therefore, the current habitat distribution of JHE’s is essential for getting knowledge about patch dynamics in JHE’s habitat. This study’s objective was to analyze patch dynamics of JHE’s habitat from 2002 until 2015 and validate habitat distribution. Previously predicted probability map (2002) of JHE’s were updated using Landsat 8 satellite images of 2015 and was validated through ground-truth checked. Results showed that the distribution of JHE’s habitat after validation is 28 patches, which is covered 4766.26 km2. The dynamics that occur in the JHE’s patch are patch lost(1 patch), patch area decreased (5 patches), patch area increased (13 patches), new patch (4 patches), and merged patch. After validation, there are six newly identified patches, and one patch area increased. The total area increased by 2156.14 km2 or 82.61% of the total area occupied by JHE’s in 2002. About 39.89% of total habitat patches were located inside the protected area. This study recommends continuing monitoring activities on habitat patches, including potential habitat patches in lowland areas, and proposing conservation activities based on habitat patch dynamics that occurred from 2002 to 2015.

Stability analysis of the coexistence equilibrium of a balanced metapopulation model

We analyze the stability of a unique coexistence equilibrium point of a system of ordinary differential equations (ODE system) modelling the dynamics of a metapopulation, more specifically, a set of local populations inhabiting discrete habitat patches that are connected to one another through dispersal or migration. We assume that the inter-patch migrations are detailed balanced and that the patches are identical with intra-patch dynamics governed by a mean-field ODE system with a coexistence equilibrium. By making use of an appropriate Lyapunov function coupled with LaSalle’s invariance principle, we are able to show that the coexistence equilibrium point within each patch is locally asymptotically stable if the inter-patch dispersal network is heterogeneous, whereas it is neutrally stable in the case of a homogeneous network. These results provide a mathematical proof confirming the existing numerical simulations and broaden the range of networks for which they are valid.

Gene-flow within a butterfly metapopulation: the marsh fritillary Euphydryas aurinia in western Bohemia (Czech Republic)

In human-altered landscapes, species with specific habitat requirements tend to persist as metapopulations, forming colonies restricted to patches of suitable habitats, displaying mutually independent within-patch dynamics and interconnected by inter-colony movements of individuals. Despite intuitive appeal and both empirical and analytical evidence, metapopulations of only relatively few butterfly systems had been both monitored for multiple years to quantify metapopulation dynamics, and assayed from the point of view of population genetics. We used allozyme analysis to study the genetic make-up of a metapopulation of a declining and EU-protected butterfly, Euphydryas aurinia, inhabiting humid grasslands in western Czech Republic, and reanalysed previously published demography and dispersal data to interpret the patterns. For 497 colony x year visits to the 97 colonies known at that time, we found annual extinction and colonisation probabilities roughly equal to 4%. The genetic diversity within colonies was intermediate or high for all assessed parameters of population genetic diversity and hence higher than expected for such a habitat specialist species. All the standard genetic diversity measures were positively correlated to adult counts and colony areas, but the correlations were weak and rarely significant, probably due to the rapid within-colony population dynamics. Only very weak correlations applied to larval nests numbers. We conclude that the entirety of colonies forms a well-connected system for their majority. Especially in its core parts, we assume a metapopulation structure with a dynamic equilibrium between local extinction and recolonization. It is vital to conserve in particular these structures of large and interconnected colonies.Implications for insect conservation: Conservation measures should focus on considering more in depth the habitat requirements of E. aurinia for management plans and on stabilisation strategies for colonies, especially of peripheral ones, e.g. by habitat restoration.

Cartographie des déterminants de l’invasion par le pin maritime, Pinus pinaster Ait., de la subéraie de Haddada dans le nord-est de l’Algérie

Plusieurs subéraies du Nord-Est algérien sont sujettes à une invasion par le pin maritime. Cette dynamique forestière qui a débuté dans les années 1980 est souvent citée parmi les facteurs de dégradation des subéraies algériennes mais n’a encore jamais fait l’objet de recherche. L’objectif de notre étude, qui porte sur le cas de la subéraie de Haddada (wilaya d’El-Tarf), était d’identifier les déterminants de l’invasion par le pin maritime, Pinus pinaster Ait., en recourant à une cartographie chorologique de facteurs tels que la pente, l’exposition et les surfaces incendiées en 1994, ainsi qu’une cartographie de la subéraie avant et après l’invasion. L’élaboration des cartes a suivi une approche géomatique complétée par des enquêtes sur le terrain. La cartographie montre que les parties envahies par le pin maritime sont celles qui ont été le plus touchées par l’incendie de 1994, ce qui correspond aussi aux pentes fortes et très fortes. La faible résilience du chêne-liège, Quercus suber, dans ces conditions a permis au pin maritime de le supplanter. Cette dynamique illustre bien le paradigme patch dynamics dans une forêt méditerranéenne, et nous renseigne aussi sur le potentiel invasif du pin maritime, s’agissant d’une espèce se révélant également invasive ailleurs dans le monde. Le changement climatique risque d’accentuer ces processus d’invasion.