Examinando por Autor "Markesteijn, Lars"

Mostrando 1 - 9 de 9

Do prey shape, time of day, and plant trichomes affect the predation rate on plasticine prey in tropical rainforests?
(Wiley, 2022-08-10) Weissflog, Anita; Markesteijn, Lars; Aiello, Annette; Healey, John; Geipel, Inga
Predation can effectively limit insect herbivores with cascading effects on plant community composition and diversity of tropical rainforests. Assessing variation in predation is therefore important to understand the mechanisms structuring complex rainforest ecosystems. Variation in predation with time of day may provide herbivores with temporal enemy-free space. Trichomes (plant hairs) may provide spatial enemy-free space by increasing climbing resistance for walking arthropod predators and by scattering bat echolocation calls. Artificial model prey is commonly used to measure predation pressure on insect herbivores. Whether model prey shape is sufficient to deceive predators and whether attacks represent actual predation however remain unresolved. We used artificial, plasticine prey to assess temporal and spatial variation in predation in two Panamanian rainforests and tested whether model prey shape is as important for prey recognition by predators as often assumed. We assessed the effect of prey shape and size, time of day, and trichomes on predation by comparing attacks on caterpillar- and humanoid-shaped figurines. We find higher nocturnal than diurnal predation in one but not the other forest, suggesting that herbivores may benefit from enemy-free space during the day in some forests. We find no evidence for an effect of trichomes on predation in the two plant species tested. Equal attack numbers on caterpillar- and humanoid-shaped objects challenge the idea that the visual resemblance of model prey alone is sufficient to deceive predators. We conclude that attacks on model prey represent a variety of responses to novel objects (e.g. exploration, aggression, possibly predation) and urge caution when interpreting their results.
Ecological differentiation in xylem cavitation resistance is associated with stem and leaf structural traits
(Plant, Cell and Environment, 2011) Markesteijn, Lars; et al.
Functional responses of mangrove fauna to forest degradation
(CSIRO Publishing, 2022-03-17) Barbanera, Ada; Markesteijn, Lars; Kairo, James; Juma, Gabriel; Karythis, Simon; Skov, Martin W.; Max Finlayson
Structural degradation of mangroves through the partial removal of trees is globally pervasive and likely to affect ecological functioning, including habitat provisioning for biodiversity. Biodiversity responses will depend on the severity of degradation, yet few studies have contraste and quantified several degradation states. Addressing this knowledge gap, we sampled faunal diversity across a range of mangrove forests in southern Kenya. Canopy cover was the strongest predictor of faunal responses among forest structural variables. Faunal abundance, species richness and biodiversity all decreased with reduction in canopy cover, and taxonomic and functional composition changed. The trophic diversity of crabs peaked at intermediate canopy cover, with degraded habitats having more generalist species and fewer specialists. Functional redundancy was unaffected by canopy thinning. The decline in functional diversity and richness of brachyuran crabs with canopy cover implies that resource-use efficiency weakens with increasing degradation. Our results are indicative of significant alterations to forest functioning with degradation, because epibenthic fauna are important regulators of mangrove ecosystem processes, including nutrient cycling and carbon.
Hydraulics and life history of tropical dry forest tree species: coordination of species’ drought and shade tolerance
(New Phytologist, 2011) Markesteijn, Lars; et al.
Increased mortality of tropical tree seedlings during the extreme 2015–16 El Niño
(Wiley, 2021-07-17) Browne, Luke; Markesteijn, Lars; Engelbrecht, Bettina M. J.; Jones, F. Andrew; Lewis, Owen T.; Manzané‐Pinzón, Eric; Wright, S. Joseph; Comita, Liza S.
As extreme climate events are predicted to become more frequent because of global climate change, understanding their impacts on natural systems is crucial. Tropical forests are vulnerable to droughts associated with extreme El Niño events. However, little is known about how tropical seedling communities respond to El Niño–related droughts, even though patterns of seedling survival shape future forest structure and diversity. Using long-term data from eight tropical moist forests spanning a rainfall gradient in central Panama, we show that community-wide seedling mortality increased by 11% during the extreme 2015–16 El Niño, with mortality increasing most in drought-sensitive species and in wetter forests. These results indicate that severe El Niño–related droughts influence understory dynamics in tropical forests, with effects varying both within and across sites. Our findings suggest that predicted increases in the frequency of extreme El Niño events will alter tropical plant communities through their effects on early life stages.
Light‐dependent leaf trait variation in 43 tropical dry forest tree species
(2007) Markesteijn, Lars; Poorter, Lourens; Bongers, Frans
Our understanding of leaf acclimation in relation to irradiance of fully grown or juvenile trees is mainly based on research involving tropical wet forest species. We studied sun-shade plasticity of 24 leaf traits of 43 tree species in a Bolivian dry deciduous forest. Sampling was confined to small trees. For each species, leaves were taken from five of the most and five of the least illuminated crowns. Trees were selected based on the percentage of the hemisphere uncovered by other crowns. We examined leaf trait variation and the relation between trait plasticity and light demand, maximum adult stature, and ontogenetic changes in crown exposure of the species. Leaf trait variation was mainly related to differences among species and to a minor extent to differences in light availability. Traits related to the palisade layer, thickness of the outer cell wall, and N(area) and P(area) had the greatest plasticity, suggesting their importance for leaf function in different light environments. Short-lived pioneers had the highest trait plasticity. Overall plasticity was modest and rarely associated with juvenile light requirements, adult stature, or ontogenetic changes in crown exposure. Dry forest tree species had a lower light-related plasticity than wet forest species, probably because wet forests cast deeper shade. In dry forests light availability may be less limiting, and low water availability may constrain leaf trait plasticity in response to irradiance.
Seedling root morphology and biomass allocation of 62 tropical tree species in relation to drought‐and shade‐tolerance
(Journal of Ecology, 2009) Markesteijn, Lars; Poorter, Lourens
Seedling traits determine drought tolerance of tropical tree species
(Biotropica, 2008) Poorter, Lourens; Markesteijn, Lars
The role of herbivorous insects and pathogens in the regeneration dynamics of Guazuma ulmifolia in Panama
(Pensoft Publishers, 2019-02-06) Solé, Raphaële; Gripenberg, Sofia; Lewis, Owen T.; Markesteijn, Lars; Barrios, Héctor; Ratz, Tom; Ctvrtecka, Richard; T. Butterill, Philip; T. Segar, Simon; A. Metz, Mark; Dahl, Chris; Rivera, Marleny; Viquez, Karina; Ferguson, Wessley; Guevara, Maikol; Basset, Yves
A significant proportion of the mortality of rainforest trees occurs during early life stages (seeds and seedlings), but mortality agents are often elusive. Our study investigated the role of herbivorous insects and pathogens in the early regeneration dynamics of Guazuma ulmifolia (Malvaceae), an important tree species in agroforestry in Central America. We reared pre-dispersal insect seed predators from G. ulmifolia seeds in Panama. We also carried out an experiment, controlling insects and pathogens using insecticide and/or fungicide treatments, as well as seed density, and compared survivorship of G. ulmifolia seeds and seedlings among treatments and relative to untreated control plots. We observed (1) high pre-dispersal attack (92%) of the fruits of G. ulmifolia, mostly by anobiine and bruchine beetles; (2) negligible post-dispersal attack of isolated seeds by insects and pathogens; (3) slow growth and high mortality (> 95%) of seedlings after 14 weeks; (4) low insect damage on seedlings; and (5) a strong positive correlation between seedling mortality and rainfall. We conclude that for G. ulmifolia at our study site the pre-dispersal seed stage is by far the most sensitive stage to insects and that their influence on seedling mortality appears to be slight as compared to that of inclement weather. Thus, the regeneration of this important tree species may depend on effective primary dispersal of seeds by vertebrates (before most of the seed crop is lost to insects), conditioned by suitable conditions in which the seedlings can grow.