Epiphyll specialization for leaf and forest successional stages in a tropical lowland rainforest

Abstract

QuestionsThe importance of tropical rainforest gap dynamics in biodiversity maintenance is not fully understood, in particular for taxa other than trees and lianas. We used epiphylls on rainforest leaves to study the importance of leaf‐ and forest‐scale succession in determining biodiversity patterns by characterizing community change with leaf age in gaps and closed‐forest habitats. We asked: (1) Do epiphylls show specialization for leaf and forest successional stages? (2) Can early‐ and late‐successional epiphyllous species be recognized at these two scales? (3) How do epiphyll presence, species richness, and cover change with leaf and forest successional stages?LocationBarro Colorado Island, Panama.MethodData were collected from 420 leaves, in three age groups and at two heights on shrubs in gaps and closed forest. We calculated turnover and nestedness components of dissimilarity to evaluate the importance of species replacement or accumulation during leaf and forest succession. Using generalized linear mixed models we determined what factors explain epiphyll species occurrence, richness and cover.ResultsClosed forest contained more liverwort and lichen specialist species than gaps. Specialist species were identified for older leaves only. Dissimilarity between leaves within age groups was dominated by turnover within and between forest successional stages. Dissimilarity between leaf age groups, at the site level, was dominated by nestedness, i.e., species accumulation. Both in forest and gaps, epiphyll presence and cover increased with leaf age for all taxa except fungi, while species richness increased only for lichens.ConclusionEarly and late forest successional stages both contribute to epiphyll species richness by harboring specialized species. Among leaf successional stages, young leaves contain a mere subset of the species found on older leaves. Epiphyll communities do not follow classic succession, in the sense of changes being driven by species replacement, but are characterized by species accumulation through time.

Directional changes over time in the species composition of tropical vascular epiphyte assemblages

“…Combining these particularities is likely to result in temporal changes driven mainly by the accumulation of species and, to a lesser degree, by species replacement. Species accumulation predominance has been previously observed in some studies of epiphylls, which also occur on an expanding habitat, such as the leaves, although probably more dynamic and ephemeral than trees (Mežaka et al, 2020).…”

Diversity begets diversity: Phorophyte and microsite relations of foliicolous lichens in the lowland rain forest at Los Tuxtlas Biosphere Reserve (Veracruz, Mexico)

“…Foliicolous lichen communities in tropical rain forests are largely structured by three factors: (a) microclimatic parameters such as relative light intensity and humidity, (b) phorophyte features such as leaf surface structure and leaf longevity and (c) primary succession (Lücking, 1998a, 1998b, 1999b, 1999c; Mežaka et al, 2020). In terms of community parameters, these factors are reflected in species composition (microclimate, phorophyte) and species richness (phorophyte, succession).…”

“…The maintenance of such high levels of diversity is ascribed to the dynamics of leaf shedding and replacement in tropical forests, which requires foliicolous lichens to continuously establish de novo microcommunities on individual leaves, thus preventing competitive exclusion (Cáceres & Lücking, 2006; Lücking, 2001a, 2008; Mežaka, Bader, Salazar‐Allen, & Mendieta‐Leiva, 2020; Rogers, 1989; Rogers & Barnes, 1986). This mechanism can be compared to the concept of intermediate disturbances fostering tree diversity in tropical forests (Connell, 1978; Molino & Sabatier, 2001), the intermediate disturbances provided by stochastically distributed tree fall gaps resulting in a mosaic of successional stages.…”

Impacto de las características foliares de helechos sobre la colonización de epífilos en la Estación de Biología Tropical Los Tuxtlas, Veracruz, México

“…Además, las hepáticas requieren de una alta y constante disponibilidad de agua para realizar su actividad fotosintética, mientras que los líquenes la realizan mejor con menor contenido de agua y se reduce con altas cantidades de agua (Coley y Kursar 1996). Finalmente, la predominancia de hepáticas en P. rhachipterygium pudo afectar el crecimiento de los líquenes, ya que al parecer pueden desplazar a éstos e incluso también a las algas (Mežaka et al, 2019).…”

“…La cobertura de epífilos en los taxa estudiados fue menor en los primeros meses e incrementó con la edad de las pinnas; y en las especies en las que fue posible evaluar las coberturas de epífilos en pinnas con edades cercanas al límite de su longevidad foliar promedio (P. rhachipterygium, D. drepanolobium, B. portoricensis y D. nodosa), incrementaron considerablemente la cobertura de epífilos en los últimos meses que les quedaba de vida a sus hojas (1.3-4.7 meses). Esto se ha observado en otros estudios, en los que la edad de la hoja ha jugado un papel importante en la cobertura de epífilos (Mežaka et al, 2019), que incrementa con el tiempo (Mueller y Wolf-Mueller, 1991;Coley y Kursar, 1996), siendo inicialmente lenta seguida por un periodo de crecimiento acelerado (Voglgruber, 2011), conforme la hoja se acerca a la senescencia (Coley et al, 1993) (Coley et al, 1993;Coley y Kursar, 1996;Voglgruber, 2011). En estos estudios los porcentajes de cobertura mencionados para las especies con menor longevidad foliar, se calcularon a los 12 y 18 meses cuando se encontraban en su máxima edad foliar; y se ha observado que la cobertura incrementa conforme las hojas se acercan más la senescencia (Coley et al, 1993).…”