The advantage of the extremes: tree seedlings at intermediate abundance in a tropical forest have the highest richness of above‐ground enemies and suffer the most damage

Abstract

K. 2016. The advantage of the extremes: tree seedlings at intermediate abundance in a tropical forest have the highest richness of aboveground enemies and suffer the most damage. Journal of Ecology, 104 (1). 90-103. 10.1111/1365-2745.12488 Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. 37!3. We found that the relationships between local and (conspecific seedling density) and community 38!scale (conspecific basal area of adult trees) abundance and both richness of above-ground 39!enemies and foliar damage were hump-shaped. Seedlings of tree species existing at intermediate 40!levels of abundance, at both local and community scales, suffered more damage and experienced 41!pressure from a greater diversity of enemies than those existing at high or low densities. 42!

Divergent parasite infections in sympatric cichlid species in Lake Victoria

“…When analysed at the level of different transmission groups of parasites, positive effects of abundance on parasite load were observed for Cichlidogyrus monogeneans, but a hump‐shaped relationship emerged for the gill copepods Lamproglena and Ergasilus . Whereas these relationships were not statistically significant, hump‐shaped relationships would be consistent with the simultaneous presence of host generalists and host specialists among the parasitic copepods, whereas the positive relationships between parasite load and host abundance point to a predominance of host specialists among the monogeneans (Bachelot et al ., ). These are promising leads for further investigations into host–parasite coevolution in this system.…”

Arbuscular mycorrhizal fungal diversity and natural enemies promote coexistence of tropical tree species

“…Herbivore insects and pathogens were likely to drive this pattern since they caused most of the observed foliar damage (Bachelot et al. ). This result is consistent with a study from Costa Rica (Bachelot and Kobe ) and a recent experimental study (Bagchi et al.…”

“…Damage included missing leaf area as well as evidence of galls, leaf mines, or necrotic spots caused by pathogens. Herbivory and pathogens caused most of the damage, whereas galls and leaf mines were less frequently observed (Bachelot et al 2015c). Proportion of leaf damage at t 0 was quantified as an ordinal variable ranging from 0 to 100 by binning damage for each seedling into 20 categories: 0-5%, 5-10%, 10-15%, …, 95-100% leaf damage.…”

Rarity and persistence

“…; but see Bachelot & Kobe ; Bachelot et al . ). To understand how chronic rarity evolves and persists, and to assess its role in species survival during crises, it is essential to identify species that are rare across their ranges over evolutionary timeframes, and the organismal traits that enable populations to survive at low density and with few individuals.…”

“…Nevertheless, rarity may also hold the key to survival during crises (Kunin 1997;Orians 1997). Not only can many species persist while chronically rare (Mace & Kershaw 1997), but others, including numerous tropical-forest trees and their seedlings, may depend on rarity to avoid being targeted by specialised herbivores and pathogens (Janzen 1970;Connell 1971;Leigh et al 2004;Lin et al 2017; but see Bachelot & Kobe 2013;Bachelot et al 2016). To understand how chronic rarity evolves and persists, and to assess its role in species survival during crises, it is essential to identify species that are rare across their ranges over evolutionary timeframes, and the organismal traits that enable populations to survive at low density and with few individuals.…”