Jack-of-all-trades paradigm meets long-term data: generalist herbivores are more widespread and locally less abundant

Abstract

Some of the most common ecological interactions are between plants and herbivorous insects, and these relationships are central to the study of ecological specialization. We address established assumptions about the positive association between local abundance and dietary specialization using a 17-year dataset on the caterpillars of Ecuador. Our long-term data include standardized plot-based samples as well as general, regional collections, allowing for investigations across spatial scales and using different indices of abundance for 1917 morphospecies of Lepidoptera from 33 families. We find that specialists are locally more abundant than generalists, consistent with a key component of the “jack of all trades, master of none” hypothesis, which has otherwise received poor to mixed support from previous studies that have mostly involved fewer species and shorter time series. Generalists achieve greater prevalence across the landscape, and we find some evidence for geographic variation in the abundance-diet breadth relationship, in particular among elevational bands. Interspecific variation in abundance also had a negative relationship with diet breadth, with specialists having more variable abundances across species. The fact that more specialized species can be both rare and common highlights the ecological complexity of specialization.

Good Things Come in Larger Packages: Size Matters for Fruit-feeding Butterfly Dispersal and Diet Breadth

“…In this study, we demonstrated the larger and less abundant species have higher dispersal patterns and broader diet breadths compared to their smaller relatives. These associations corroborate the evidence found in a long-term study from Ecuador, in which generalist species are widespread and locally less abundant [18,19,20]. Further studies are required to confirm the causal mechanisms operating to generate the observed patterns, and to test the correlations between fine-scale movements and large-scale dispersal.…”

“…From these studies, the common expectation is that "a jack of all trades is a master of none," which, in an ecological context, refers to the idea that generalists might be able to consume a wide range of resources but will not be particularly well adapted to any of them [17]. In this context, most studies show that specialized species tend to be smaller [18,19], more abundant, and more spatially restricted than their larger relatives [20,19]. However this pattern is not universal, and some studies report that such relationships do not exist for some insect clades [21,22].…”

“…However this pattern is not universal, and some studies report that such relationships do not exist for some insect clades [21,22]. Understanding how diet breadth mediates these species trait relationships, such as body size, abundance, and dispersal ability, can contribute in identifying factors influencing community composition, which may also inform conservation programs, especially in tropical regions [19,20].…”

Effects of occupancy estimation on abundance–occupancy relationships

“…Considering these species differences, especially in terms of geographic ranges and environmental niche, when estimating occupancy is important as it can provide a more realistic depiction of abundance-occupancy relationships. For example, taking these species differences into account will improve our assessment of the effects of specialist and generalist species on abundanceoccupancy relationships [5,44] given that specialist species generally have narrower environmental niches and smaller geographic ranges than generalist species [45,46]. The positive relationship between species environmental niche and geographic range size [27,28] suggests that both factors are intrinsically related and are important to determine species occurrences.…”

Time will tell: Larger and less abundant fruit-feeding butterflies (Lepidoptera: Nymphalidae) are synchronized with food availability in the Brazilian Cerrado

“…One possible explanation is that the higher energetic demand of larger species constrains them to occur in a narrow time period when optimal resources are available (Brown et al 2004;Ribeiro & Freitas 2011). Moreover, small-bodied species tend to have shorter lifespans, despite their wider temporal distribution, greater abundances, and narrower larval diet breadths (Hjalmarsson et al 2015;Freire-Jr. et al 2021.a;Sudta et al 2022). Although the association between diet breadth and temporal distribution is poorly understood in butter ies, our expectation is that the temporal distribution of smaller and more specialized butter y species will be less restricted throughout the year compared to their larger relatives (Pozo et al 2008;Ribeiro & Freitas 2011;Freire Jr. & Diniz 2015).…”