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. 2025 Feb;245(4):1762-1773.
doi: 10.1111/nph.20316. Epub 2024 Nov 28.

Fossil insect-feeding traces indicate unrecognized evolutionary history and biodiversity on Australia's iconic Eucalyptus

L Alejandro Giraldo  1 , Peter Wilf  1 , Michael P Donovan  2 , Robert M Kooyman  3   4   5 , Maria A Gandolfo  6   7
Affiliations

Fossil insect-feeding traces indicate unrecognized evolutionary history and biodiversity on Australia's iconic Eucalyptus

L Alejandro Giraldo et al. New Phytol. 2025 Feb.

Abstract

Fossilized plant-insect herbivore associations provide fundamental information about the assembly of terrestrial communities through geologic time. However, fossil evidence of associations originating in deep time and persisting to the modern day is scarce. We studied the insect herbivore damage found on 284 Eucalyptus frenguelliana leaves from the early Eocene Laguna del Hunco rainforest locality in Argentinean Patagonia and compared damage patterns with those observed on extant, rainforest-associated Eucalyptus species from Australasia (> 10 000 herbarium sheets reviewed). In the fossil material, we identified 28 insect herbivory damage types, including 12 types of external feeding, one of piercing-and-sucking, five of galls, and 10 of mines. All 28 damage types were observed in the herbarium specimens. The finding of all the fossil damage types on extant Eucalyptus specimens suggests long-standing associations between multiple insect herbivore lineages and their host genus spanning 52 million years across the Southern Hemisphere. This long-term persistence, probably enabled through niche conservatism in wet eucalypt forests, demonstrates the imprint of fossil history on the composition of extant insect herbivore assemblages. Although the identities of most insect culprits remain unknown, we provide a list of Eucalyptus species and specific population locations to facilitate their discovery, highlighting the relevance of fossils in discovering extant biodiversity.

Keywords: Gondwana; Myrtaceae; eucalypts; hidden biodiversity; host‐tracking; leaf mining; niche conservatism; paleobotany.

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Conflict of interest statement

None declared.

Figures

Fig. 1
Fig. 1
Geographic location of the early Eocene Laguna del Hunco locality (yellow star), the source of the fossil Eucalyptus frenguelliana material, alongside the distribution of extant rainforest‐associated Eucalyptus species reviewed from herbarium specimens (pink areas) for insect herbivore damage comparable with the fossils. Maps modified from the Australasian Virtual Herbarium (https://avh.chah.org.au/).
Fig. 2
Fig. 2
Paired examples of mining in fossil Eucalyptus frenguelliana leaves from Laguna del Hunco (first of pair) and corresponding analogs on extant Eucalyptus species (second of pair). Note that the paths of the mines begin narrow and progressively widen, thus indicating the directions of the mines. Museum codes for the fossils and catalogue codes for the herbarium specimens are given in Supporting Information Notes S1 and Table S1. (a, b) Mines occurring alongside the midvein, with constant width (newly described DT422) (b E. tereticornis). (c, d) Thin, highly serpentine mines with elliptical terminal chambers (DT171) (d E. cloeziana). (e, f) Serpentine mines crossing the midvein (DT94) (f E. decolor). (g, h) Thread‐like mines with wider phase after crossing the midvein (DT41) (h E. cloeziana). (i, j) Short, curvilinear mines deeply embedded into the leaf tissue (DT139) (j E. melliodora). (k, l) Short, curvilinear mines with massive reaction tissue and associated leaf shape deformation (DT185) (l E. crebra). (m, n) Strongly folded serpentine mines, with paths determined by secondary veins (DT92) (n E. major). (o, p) Bifurcating mines with smooth borders (DT207) (p E. punctata). (q, r) Short mines circumscribed by secondary veins and elliptical terminal chambers (DT210) (r E. robusta). (s, t) Short, curvilinear mines terminating at the leaf margin (DT90) (t E. major).
Fig. 3
Fig. 3
Paired examples of hole feeding (a–d), margin feeding (e–l), surface feeding (m–p), skeletonization (q–t), piercing‐and‐sucking (u–v), and galling (w–cc) in fossil Eucalyptus frenguelliana leaves from Laguna del Hunco (first of pair) and corresponding analogs on extant Eucalyptus species (second of pair). Museum codes for the fossils and catalogue codes for the herbarium specimens are given in Supporting Information Notes S1 and Table S1. (a, b) Small circular (DT1; uppermost arrows) and polylobate (DT3; lowermost arrows) holes (b E. resinifera). (c–d) Elongate holes (DT8) (d E. major). (e, f) Excisions removing leaf apices (DT13) (f E. crebra). (g, h) Excisions into the leaf margin, either shallow (DT12; uppermost arrows) or reaching the midvein (DT14; lowermost arrows) (h E. acmenoides). (i, j) Deeply trenched excisions (DT15) (j E. fibrosa). (k, l) Consecutive, nearly perfect semicircular excisions along the leaf margin (DT81) (l E. grandis). (m, n) Circular surface abrasions with thick reaction rims (DT31) (n E. robusta). (o, p) Polylobate surface abrasions with thick reaction rims (DT30) (p E. fibrosa). (q, r) Skeletonized areas without reaction rims (DT16) (r E. michaeliana). (s, t) Skeletonized areas with thick reaction rims (DT17) (t E. tereticornis). (u, v) Circular scale insect (Diaspididae) covers occurring in clusters (DT77) (v E. notabilis). (w–y) Featureless galls occurring in the leaf lamina (DT32; middle arrow in w and lowermost gall in x), alongside the midvein (DT33; lowermost arrow in w and galls in y), or alongside secondary veins (DT34; uppermost arrow in w and uppermost gall in x) (x E. punctata; y E. propinqua). (z, aa) Thick, ellipsoidal galls with internal carbonized cores (DT49) (aa E. punctata). (bb, cc) Lenticular galls occurring along midvein (DT85) (cc E. tereticornis).
Fig. 4
Fig. 4
Occurrences of insect herbivory damage types found in Eucalyptus frenguelliana leaf fossils from Laguna del Hunco (columns) on extant Eucalyptus subgenera, from our herbarium survey. Phylogenetic relationships among subgenera are summarized from Thornhill et al. (; four unsampled subgenera not included). Labels beneath subgenera indicate the number of herbarium sheets reviewed for that subgenus (Supporting Information Dataset S3). SK, skeletonization; P&S, piercing‐and‐sucking.
Fig. 5
Fig. 5
Literature survey totals of representative species‐level associations of insect herbivores and Eucalyptus host plants described vs described and illustrated (drawing or photograph) from 1961 to 2020. Each bar represents the number of unique insect‐Eucalyptus species‐pair associations in the survey (Supporting Information Dataset S4), colored by Functional Feeding Group (FFG; external feeding encompasses hole, margin, and surface feeding, as well as skeletonization) following Labandeira et al. (2007). Only leaf‐feeding associations are depicted here (i.e. wood boring is excluded), but see Dataset S4 for the full list of associations.
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References

    1. Adam P. 1994. Australian rainforests. Melbourne, Vic., Australia: Oxford University Press.
    1. Adroit B, Zhuang X, Wappler T, Terral J‐F, Wang B. 2020. A case of long‐term herbivory: specialized feeding trace on Parrotia (Hamamelidaceae) plant species. Royal Society Open Science 7: 201449. - PMC - PubMed
    1. Aragón E, Mazzoni MM. 1997. Geología y estratigrafía del complejo volcánico piroclástico del Río Chubut medio (Eoceno), Chubut, Argentina. Revista de la Asociación Geológica Argentina 52: 243–256.
    1. Ash J. 1988. The location and stability of rainforest boundaries in north‐eastern Queensland, Australia. Journal of Biogeography 15: 619–630.
    1. Bairstow KA, Clarke KL, McGeoch MA, Andrew NR. 2010. Leaf miner and plant galler species richness on Acacia: relative importance of plant traits and climate. Oecologia 163: 437–448. - PubMed

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