Figure of the decline of caterpillars collected in ACG over time since the standardisation of the paratxonomist workforce in 2005 (black line). The red line tracks the proportion of the collected caterpillars that were parasitised - also declining.
Lepidopteran abundance in ACG is declining (Janzen and Hallwachs 2021). While the trajectory of species within individual families may differ in the specifics from the overall trend (Figure X, Janzen and Hallwachs 2021) it is clear that in most cases, once the parataxonomist workforce stablised in ~2005 (that is – the individuals in the forests of ACG collecting caterpillars and leaves), there has been a marked decline collections of lepidoptera and their fly and wasp parasitoids. Over this same time-period, the seasonal rains in the dry forest and low-elevation rain forest have become more erratic and the temperatures of air and soil are creeping upwards in all forest ecosystems – especially the high elevation rain forest and cloud forest (Janzen and Hallwachs 2021, Smith 2023). Thus, although the evident declines documented here may not solely due to climate change – the rapidity and force of the abiotic changes to these forests are involved in these declines. Some taxa may be capable of moving upslope or towards the wetter forests of the Caribbean (Warne et al 2020), but many will, or can, not. These observations parallel other observations of reductions in the diversity and abundance of caterpillars and their parasitoids within a protected area that are at least partially due to changing climate (Salcido et al 2020).
Bipartite figure of relationships between Erebidae caterpillars and their host plants in ACG. The bipartite network of Erebidae species and host plants had a high network-wide estimate of specialisation (H2' = 0.894 Blüthgen et al., 2006) where values close to 0 indicate extreme generalization and those closer to 1 indicate specialization (Blüthgen et al., 2006). Specialisation can be visualized in Figure y by the broad blue links that connect some of the most common species of caterpillar to their host plant. For example, two species of Phaeoblemma (P. apicata and P. dares) were found only on two species of the Fabaceae, Senna (S. obtusifolia and S. papillosa). Smaller links flow out of these Senna to indicate that these species have also been, much more infrequently, food for 17 other species of Erebidae in this matrix. In another example, two Dysschema species (D. jansonis and D. leucophaea) both consume the Asteraceae Lepidaploa tortuosa – but this host plant has been found associated with 32 other species in the reduced matrix.
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Very honored/excited to take part in this paper analysing & releasing 🐛 caterpillar rearing info from #ACG #CostaRica collected by #DanJanzen and #WinnieHallwachs and the #parataxonomists of @gdfcf.bsky.social
doi.org/10.3389/fevo...
Figures from data available at doi.org/10.5683/SP3/...
