The effects of flooding disturbance on the distribution and behaviour of riparian arthropods along a lowland gravel river

This Ph.D.-thesis aimed to address which environmental factors influence the assemblage structure of mobile, riparian arthropods along spatially structured river banks of a rain-fed, lowland gravel river, the Common Meuse. As riverine ecosystems are basically non-equilibrium, dynamic ecosystems, mainly flow regimes and flood pulse characteristics are expected to shape both the distribution and behaviour of its inhabitants. The river banks along the Common Meuse are (in)frequently disturbed by flood events and liable to extreme microclimatological conditions. Hence, functional life-history traits of the present species, particularly spiders (Araneae) and carabid beetles (Carabidae), supposedly affect species composition as well. Moreover, organisms occurring within a highly structured system and which are repeatedly exposed to flooding disturbance, are expected to have evolved or adjusted their behavioural responses in accordance with their functional life-history characteristics such as habitat affinity and mobility. Correspondingly, less mobile species are expected to show variation in their spatial genetic structure as well. Based on an intensive pitfall survey, increased anthropogenic alterations of water discharges were shown to cause the loss of stenotopic, xerothermophilic and less mobile riparian arthropods. Next to it, the results of two field experiments indicated that movement decisions of two sympatric wolf spiders (Lycosidae) were guided, particularly, by factors related to their population of origin (side of the river; either genetics or experience). A stenotopic riparian wolf spider, however, relied more on individual information (e.g. visual signals) and showed a higher degree of behavioural plasticity. This might increase the beneficiality of flood-avoiding behaviour. By using Amplified Fragment Length Polymorphism (AFLP) markers, the genetic population structure of the highly stenotopic wolf spider Pardosa agricola (Thorell, 1856) was studied. Nearby populations were less differentiated genetically than populations on different sides of the river, indicating the importance of functional connectivity along the riparian corridor. River restoration and the rehabilitation of the riparian corridor should generate the required heterogeneity at the river bank level, hence increasing the sustainability of dynamic lowland river systems and realizing the conservation of vulnerable riparian arthropods. River management should consider the management of the alluvial hinterland as well to provide suitable refuges during flooding

Boomkikker en kamsalamander in Vlaanderen : eindelijk van de ondergang gered?

Boomkikker en kamsalamander komen omwille van hun Europese bescherming regelmatig onder de aandacht. Er worden al geruime tijd inspanningen gedaan om deze soorten te beschermen, maar die waren niet altijd even succesvol. Het is pas sinds 2007 dat er dankzij de inzet van vrijwilligers met grootschalige acties en gericht beheer successen worden geboekt. Anno 2018 worden eindelijk nieuwe soortbeschermingsprogramma’s (SBP’s) voor beide soorten in Vlaanderen opgemaakt. Het moment bij uitstek om een overzicht te geven van hoe het beide de afgelopen jaren verging, en welke initiatieven echt het verschil hebben gemaakt, met aandacht voor wat zeker niet mag ontbreken in de nieuwe SBP’s

Relaciones culturales filipino-persas (I): las Rubaiyat de Manuel Bernabé

Life history trade-offs are a key notion in evolutionary biology, notably for understanding how selection shapes the diversity of traits among species. Despite the frequent study of such trade-offs, few studies synchronously investigate the effects of multiple factors, such as niche specialization and adaptation to harsh environments. We compared reproduction (fecundity and egg quality) in two sympatric couples (one habitat generalist and one specialist) of congeneric wolf spider species, in both Arctic and temperate habitats. We found that specialist species at both latitudes invested more in clutch size than did generalist species. We interpret this result as an optimization of clutch production. In the Arctic, the specialist was able to invest in fecundity with increasing body size at a much higher rate than the generalist species. In the temperate habitat, both species showed similar strategies: they increased quantity and quality of offspring relative to body size at the same rate. These results are consistent with the hypothesis that Arctic species must develop distinct strategies in order not to overlap each other’s ecological niches as a consequence of limited food resources or niche space. We emphasize the need to test the role of plasticity and environmentally mediated effects of competition on arthropod fitness

Boomkikker en Kamsalamander in Vlaanderen : eindelijk van de ondergang gered?

Boomkikker en Kamsalamander zijn amfibieën die omwille van hun Europese bescherming regelmatig onder de aandacht komen. Ze prijken vaak op infopanelen en folders als ambassadeur voor een gebied of een natuurproject. Er worden al geruime tijd inspanningen gedaan om deze soorten te beschermen. Maar die waren lange tijd niet altijd even succesvol. Het is pas sinds 2007 dat er dankzij grootschalige acties en gericht beheer successen worden geboekt. Dit voornamelijk dankzij lokale en provinciale initiatieven. Sinds 2015 worden soortenbeschermingsprogramma’s (SBP’s) op niveau Vlaanderen opgemaakt. Zijn dergelijke SBP's eindelijk het stapje hogerop? In dit rapport het relaas over het wel en wee van beide soorten met een bespreking van succesvolle maatregelen waarop toekomstige SBP’s voor Boomkikker en Kamsalamander verder kunnen bouwen

Integrating environmental conditions and functional life-history traits for riparian arthropod conservation planning

River banks are naturally disturbed habitats, in which local flood events and the landscape structure are expected to govern riparian species assemblages. Not solely effects of flooding per se, but also related changes in vegetation structure will affect species’ distribution. By elucidating the relationships between species’ occurrence and multivariate habitat conditions on a restricted spatial scale, insight into conservation strategies to preserve riparian species is gained. Ordination and grouping methods revealed important environmental and functional trait constraints on species composition of predatory riparian arthropod assemblages. Mainly flooding disturbance appeared to affect spider and carabid beetle species composition. Habitat affinity and dispersal ability were retained as important traits explaining similarity between arthropod assemblages. River banks similar in species composition differed in absolute and functional group species richness. Furthermore, Poisson regressions demonstrated the importance of variation in discharge regime, sediment composition and vegetation structure for the preservation of rare riparian arthropods. Whereas hygrophilic species benefited from increased vegetation cover, xerothermophilic specialists were favoured by increased flooding disturbance. In contrast to flight-active riparian carabids occurring throughout the river system, especially cursorial spiders are expected to go extinct under increased anthropogenic alterations of discharge regimes. We show the importance of a dynamic and evidence-based approach of river management on a local scale to preserve vulnerable riparian arthropods. In general, river restoration should generate the required heterogeneity in environmental conditions (e.g. dynamic processes) at the river bank level, thereby increasing the sustainability of riverine landscapes. More-over, we argue that the understanding of functional responses towards environmental factors results in general and widely applicable guiding concepts for species conservation

Verspreiding en ecologie van doornsprinkhanen (Orthoptera: Tetrigidae) in het voormalig zandwinningsgebied Bos van Aa (Zemst)

Dit artikel beschrijft het voorkomen van doornsprinkhanen in Bos van Aa, met aandacht voor hun fenologie en verspreiding. Een uitgebreide dataset van omgevingsvariabelen laat ons toe om dieper in te gaan op de specifieke ecologie van elke soort en aanbevelingen te doen naar beheer van de aanwezige biotopen

Plasticity in flood-avoiding behaviour in two congeneric riparian wolf spiders

The ecological effects of disrupted flooding are known to be pernicious for the occurring riparian fauna. As flooding disturbance is argued to structure species assemblages, behavioural aspects may be affected just as well. Generally, eurytopic inhabitants possess a well-developed dispersal ability allowing frequent recolonization, whereas specialized stenotopic species are expected to be adapted to these stress regimes. This study aims at determining whether flooding induces different behavioural responses in two congeneric wolf spider species. Variation in flood-avoiding behaviour was evaluated by means of individual tests performed under different ambient conditions. We considered sheltering behaviour preceding flooding, a direct flight reflex induced by the flood event, an escape reaction away from the rising water and submersion tolerance. Our findings indicated clear flood-avoiding behaviour for both species, yet a higher degree of plasticity in individual behaviour for a riparian wolf spider (Pardosa agricola) in contrast to a generalist species (P. amentata). Nonetheless the former species systematically reacted under different ambient conditions, a generalist shifts responses, displaying a higher degree of between-individual variation. Submersion tolerance was equivalent, emphasizing similar morphological characteristics. We argue habitat specialization and/or experience with local conditions to influence behavioural responses in order to optimize long-term persistence under flood stress. Future studies of behavioural variation should consider temporal variation in species condition, thus employing distinct populations thriving under different local stress regimes