Rich and Specialized Plant-Insect Associations in a Middle–Late Paleocene (58–60 Ma) Neotropical Rainforest (Bogotá Formation, Colombia)

Abstract

Plant predation by insects is a major driver of high plant diversity in modern tropical forests. Previous reports of leaf damage in middle-late Paleocene Neotropical rainforests of Cerrejón, Colombia, show that leaf herbivory was abundant but of low diversity, mainly inflicted by generalized feeders. Here, we present and describe plantinsect associations in leaf fossils from the middle-late Paleocene Bogotá Formation, central Colombia, to test whether the high abundance and low richness of insect damage typified early evolving Neotropical rainforests. The Bogotá flora records the highest richness and frequency of insect-damage associations among comparable Paleocene floras in North America, Patagonia, and Europe, as well as the highest number of leaf mines and galling associations. These results indicate that by the middle-late Paleocene, plant-insect herbivore interactions were much more intense and host-specialized in Neotropical rainforests of the Bogotá region than elsewhere. The rich and frequent galling associations, a distinctive feature of the Bogotá flora, are consistent with the preferential use of canopy leaves by galling insects seen in modern Neotropical rainforests. Our results also indicate differences in plant-insect associations among Paleocene Neotropical rainforests, perhaps reflecting a geographically heterogeneous ecological recovery from the end-Cretaceous ecological crisis. Plant insect-associations in the Bogotá flora also suggest a deep historical context for negative densitydependence as a potential driver (and maintainer) of the high plant diversity observed in modern Neotropical rainforests.

Generating and testing hypotheses about the fossil record of insect herbivory with a theoretical ecospace

“…Estimates of damage type diversity may be biased toward assemblages that have been described most recently under a scenario in which existing damage types are have increased in number (Dos Santos et al, 2020;Xiao et al, 2021). However, Giraldo et al (2021) found that this is not the case: a more conservative approach toward splitting damage types does not yield a noticeable 49 decrease in damage type diversity as standardized through rarefaction.…”

“…To discern whether this great increase in damage type diversity with heightened sample coverage is truly unique to angiosperm-dominated assemblages, far more non-angiosperm-dominated assemblages will need to be evaluated for insect herbivory. Insect herbivory from these four assemblages was described within the last ten years (Wappler et al, 2012;Möller et al, 2017;Giraldo et al, 2021). Estimates of damage type diversity may be biased toward assemblages that have been described most recently under a scenario in which existing damage types are have increased in number (Dos Santos et al, 2020;Xiao et al, 2021).…”

“…Some floral assemblages do not contain any seeds and other non-foliar specimens, and of those that do, the non-foliar specimens may or may not be included in published datasets. Within angiosperm-dominated floras, ferns, gymnosperms, and monocots may (Robledo et al, 2018;Giraldo et al, 2021) or may not (Azevedo Schmidt et al, 2019;Currano et al, 2019) be examined. Criteria for inclusion in comparative analyses can even vary within the same research group, with some workers using a wider definition of foliage that includes needles, liverworts, phyllids, photosynthetic wings of seeds, and even flattened horsetail axes (Prevec et al, 2009;Labandeira et al, 2018), and others using a narrower definition restricted to multi-veined broad leaves or leaves with a defined midvein (Schachat et al, 2014(Schachat et al, , 2015(Schachat et al, , 2018(Schachat et al, , 2020.…”

Ecology and Evolution of Gall-Inducing Arthropods: The Pattern From the Terrestrial Fossil Record

“…This pattern indicates that, although early Neotropical rainforests had high herbivore pressure, the incidence of host-specialist associations from mining and galling was unusually low. However, the Bogotá flora from central Colombia, approximately 1 million years younger than the Cerrejón flora, displays much greater mining and galling associations and has the highest number of miner and galling DTs than any flora of comparable age in North America (Giraldo et al, 2021).…”

“…A 58-million-year-old flora from the Cerrejón Fm from La Guarjira Province of northernmost Colombia represents a very early record of a Neotropical rainforest (Wing et al, 2009; also see Carvalho et al, 2021;Giraldo et al, 2021). However, although the rate of herbivory of well-preserved leaves was high, at 50%, the richness of DTs among all FFGs in both bulk samples and on individual leaf specimens show rather low levels.…”