Insect herbivory declines with forest fragmentation and covaries with plant regeneration mode: evidence from a Mexican tropical rain forest

Abstract

The consequences of tropical forest fragmentation on herbivory are poorly understood. The limited evidence suggests that forest fragmentation can have positive, negative or neutral effects on herbivory. Inconsistencies may be partly explained by plant interspecific variation and differential responses related to plant life history. In this study we examined the effects of forest fragmentation and plant regeneration mode (shade‐tolerant and light‐demanding species) on sapling herbivory using a large sample of the community (97 species, representing 25% of the woody flora of the study site), and a subset of species shared by forest fragments and continuous forest. For the latter, we also analyzed the effects of species identity on variation in herbivory. Also, for the shared species we used two techniques to measure herbivory: standing herbivory (i.e. instantaneous, actual damage) and cumulative herbivory (i.e. damage, accumulated over time, on initially intact leaves). Insect herbivory was the predominant type of damage in the two forest types, and standing herbivory at both the community and the shared species level was significantly higher in continuous forest than in fragments. Considering shared species, both standing and cumulative herbivory were significantly higher in light‐demanding than in shade‐tolerant species. Cumulative herbivory also showed a significant interaction between forest fragmentation and plant regeneration mode, whereby a significant decline in herbivory in fragments was driven by reduced herbivory in shade‐tolerant species, whereas for light‐demanding species herbivory did not change significantly, due to contrasting species‐specific responses. We conclude that tropical forest fragmentation reduces insect herbivory, but this depends on plant regeneration mode and species identity. These changes could have effects on plant regeneration and diversity in forest fragments via long‐term demographic consequences.

Gall wasp community response to fragmentation of oak tree species: importance of fragment size and isolated trees

“…Our results are initially counterintuitive, and contrast with the predictions of Holt's (1996) model and patterns observed in other herbivore systems (e.g., Ruiz-Guerra et al 2010). Landscape fragmentation reduces the connectivity between patches, diminishing richness of organisms living in smaller patches due to higher rates of extinction, and reducing occupancy in the most isolated sites through low rates of recolonization (Hanski 1999).…”

“…Second, the effects of habitat fragmentation on local patterns of cynipid communities are likely to be independent of patterns at larger regional scales (e.g., Cornell 1985), paralleling patterns that have been seen in other galling herbivore communities (Araù jo et al 2013). It remains to be seen whether the patterns described for gall inducers differ from those observed in other herbivore guilds because of specific properties of gall-associated communities (Ruiz-Guerra et al 2010). …”

“…Forest fragmentation can modify the composition, abundance and distribution of herbivores such as gall inducing insects (Didham et al 1996, Chust et al 2007, Ruiz-Guerra et al 2010, Kaartinen and Roselin 2011. In general, habitat fragmentation affects herbivore diversity through their biotic interactions (Tscharntke 1992, Didham et al 1996, Fagan et al 1999) with natural enemies (top-down effects) (Holt 1996, Askew et al 2013) and host plants (bottom-up effects) (Tscharntke et al 2002).…”

Not all in the same boat: trends and mechanisms in herbivory responses to forest fragmentation differ among insect guilds

“…Arnold and Asquith 2002;Valladares et al 2006;Vásquez et al 2007;Simonetti et al 2007;Savilaakso et al 2009;Ruiz-Guerra et al 2010). …”

Mosaicos sucessionais em florestas tropicais: efeitos sobre o forrageio e deposição de fezes pela anta Tapirus terrestris (Perissodactyla: Tapiridae)

“…Nos estágios iniciais de sucessão, 93% da comunidade de insetos é composta por herbívoros e esta proporção diminui ao longo do processo de sucessão (Schulze et al 2002). Além disso, a taxa de herbivoria por insetos é maior sobre plantas de crescimento rápido do que em plantas de crescimento lento (Ruiz-Guerra et al 2010, Bach 1990), declinando com a posição sucessional das espécies (Poorter et al 2004). Embora o impacto da herbivoria por grandes mamíferos herbívoros sobre a regeneração tenha sido amplamente estudado ), há poucos estudos que testaram o efeito do estádio sucessional sobre a intensidade de forrageio para este grupo.…”