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opencc-by-4.0Mar 2024View details →

What do we know about the missing millions of Earth's insect species: evidence from Australian tropical rainforest bark beetles?

Only 20% of the estimated five million species of insects on Earth are named despite over 240 years of taxonomy. Yet insects are poorly represented in protected area assessments, and insect declines are of concern globally. Here we explore how to increase the discovery of new species and understanding of this group through analysis of 10,097 tropical rainforest bark beetles (Scolytinae) from eight different ecological studies using beetles between 2000 and 2018 in the Australian Wet Tropics. Of the 107 species identified, 58 are undescribed: an increase of 35% on the 166 species known from Australia. As hypothesised, new species are significantly smaller, less abundant and less widespread than described species making them more extinction prone than named species. Rarefaction indicates doubling sampling would increase the number of species by 17. Flight Interception Traps (FIT) collected 84% of individuals and 98% of species confirming the effectiveness of a single sampling method for some beetles. Increased locations and collection from the canopy may sample further species rather than additional collecting methods.  Scolytines are relatively well studied with a cadre of taxonomists at the forefront of using modern methods to resolve formerly intractable groups. These new species are more likely to be named than others in many other beetle groups where taxonomy has largely stalled. To increase species description rates and to avoid most species becoming extinct before being named, we call on taxonomists to use new character systems provided by DNA methods and to look at working with Artificial Intelligence tools.

opencc-zeroJul 2022View details →

Data from: Out of the tropics: Macroevolutionary size trends in an old insect order are shaped by temperature and predators

Global body size distributions are shaped by selection pressures arising from biotic and abiotic factors such as temperature, predation and parasitism. Here, we investigated the ecological and evolutionary drivers of global latitudinal size gradients in an old insect order (Odonata; dragonflies and damselflies). Phylogenetic comparative analyses revealed that global size variation of extant taxa is negatively influenced by both regional avian diversity and temperature. Interestingly, fossil data show that the relationship between wing size and latitude has shifted: latitudinal size trends had initially negative slopes but became shallower or positive following the emergence of birds 150 MYA. These changing size-latitude trends over geological time were likely driven by bird predation and high dispersal ability of large dragonflies. Our results therefore suggest that latitudinal size gradients were shaped by temperature but also by predators driving the dispersal of large-sized clades out of the tropics and in to the temperate zone.

opencc-zeroAug 2022View details →

Tropical–temperate comparisons in insect seed predation vary between study levels and years

The biotic interaction hypothesis, which states the species interaction becomes stronger in the tropics, is deeply rooted in classic ecological literature and widely accepted to contribute to the latitudinal gradients of biodiversity. Tests in latitudinal insect-plant interaction have emphasized leaf-eating insects on a single or a few plant species rather than within an entire community and mixed accumulating evidence, leaving the biotic interaction hypothesis disputed. We aimed to test the hypothesis by quantifying seed predation by insects in a pair of tropical and temperate forest communities with similar elevations. We applied a consistent study design to sample pre-dispersal seeds with systematically set seed traps in 2019-2020 and examined internally feeding insects. The intensity of seed predation was measured and further applied to tropical versus temperate comparison at two levels (cross-species and community-wide). Our results showed every latitudinal pattern associated with different study levels and years, i.e., negative (greater granivory in the tropics in community-wide comparison in 2020), positive (less granivory in the tropics in community-wide and cross-species comparison in 2019), and missing (similar level of granivory in the tropics in cross-species comparisons in 2020). The cross-species level analyses ignore differences among species in seed production and weaken or even lose the latitudinal trend detected by community-wide comparisons. The between-year discrepancy in tropical-temperate comparisons relates to the highly variable annual seed composition in the temperate forest due to mast seeding of dominant species. Our study highlights that long-term community-level researches across biomes are essential to assess the latitudinal biotic interaction hypothesis.

Fig. 1 in Hymenopteran parasitoids associated with scale insects (Hemiptera: Coccoidea) in tropical fruit trees in the eastern Amazon, Brazil

Fig. 1. Interactions between species of scale insects and parasitoids with the total number of interactions with each species of host plant (Jun 2014 to Aug 2015) at Maranhão Island, Maranhão, Brazil.

Fig. 6 in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 6. Variation in Equitability (J) and Berger-Parker dominance (DBP) of Diptera (A) and Auchenorrhyncha (B) during 12 months of sampling over six 500 m elevation zones at Doi Inthanon in 2014. Values of J (bars) and DBP (lines) were computed in PAST and 95% confidence intervals obtained by bootstrapping using 9999 random samples. In Kruskal-Wallis H-tests there was a significant difference between the medians for Berger-Parker dominance in Diptera (H = 26.7, p <0.01) and Auchenorrhyncha (H = 14.9, p <0.01). Equitability was significantly different for Diptera (H = 36.5, p <0.01) but not for Auchenorrhyncha (H = 10.7, p = 0.0582).

Fig. 10 in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 10. Variation in Mean Monthly Turnover (βwM) of Diptera (A) and Auchenorrhyncha (B) during 12 months of sampling over six 500 m elevation zones at Doi Inthanon in 2014. The mean value of βwM in each elevation zone ± standard error is indicated. Note that the vertical axis does not extend to zero. In Kruskal-Wallis H-tests there was a significant difference between the medians for Diptera (H = 29.0, p <0.01) and Auchenorrhyncha (H = 22.1, p <0.01).

Fig. 2 in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 2. Observed species richness (Sobs) of Diptera and Auchenorrhyncha trapped in six elevation zones over 12 months sampling at Doi Inthanon in 2014. Diptera, open circles; Auchenorrhyncha, closed circles.). In Kruskal-Wallis H-tests there was a significant difference between the medians for Diptera (H = 22.1, p <0.01) and Auchenorrhyncha (H = 14.3, p <0.05).

Fig. 1. Relative abundance, A in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 1. Relative abundance, A* (number of individuals caught. trap-1. month-1) of Diptera and Auchenorrhyncha trapped in six elevation zones over 12 months sampling at Doi Inthanon in 2014. Standard errors indicated. Note log10 scale. Data were fitted to a linear regression model in PAST; Diptera, open circles (r2 = 0.8567, p = 0.0081); Auchenorrhyncha, closed circles (r2 = 0.3182, p = 0.2434). In Kruskal-Wallis H-tests of untransformed data there was a significant difference between the medians for Diptera (H = 29.3, p <0.01) but not for Auchenorrhyncha (H = 3.3, p = 0.657).

Fig. 8 in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 8. Variation in species turnover measured as βw of Diptera (a) and Auchenorrhyncha (b) during 12 months of sampling over six 500 m elevation zones at Doi Inthanon in 2014. Pairwise calculations of βw between each quadrat of a grid of elevation and month with the quadrat with maximum species richness (April/1,500–2,000 m quadrat for Diptera and June/500–1,000 m quadrat for Auchenorrhyncha) were mapped using the multiquadric gridding algorithm in the gridding module of PAST. Values of βw (indicated by colour scale bar) vary between 0 (complete identity) and 1.0 (complete non-identity). Data are not available for January and February at <500 m and 500–1,000 m.

Fig. 3. Relative abundance, A in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 3. Relative abundance, A* (number of individuals caught. trap-1. month-1) of Diptera and Auchenorrhyncha over 12 months sampling at Doi Inthanon in 2014. Standard errors indicated. Note log10 scale. In Kruskal-Wallis H-tests of untransformed data there was a significant difference between the medians for Diptera (H = 24.5, p <0.05) and Auchenorrhyncha (H = 34.3, p <0.01).

Fig. 9 in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 9. Spatiotemporal variation in species turnover measured as Mean Local Turnover βwL of Diptera (A) and Auchenorrhyncha (B) trapped during 12 months of sampling over six 500 m elevation zones at Doi Inthanon in 2014. Data were plotted on a grid of elevation zone (vertical axis) and months (horizontal axis) and mapped using the multiquadric gridding algorithm in the gridding module of PAST. Values of βwL (indicated by colour scale bar) vary between 0 (complete identity) and 1.0 (complete non-identity). Data are not available for January and February at <500 m and 500–1,000 m.

Fig. 7 in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 7. Monthly variation in Equitability (J) of Diptera assemblages during 12 months of sampling over six 500 m elevation zones at Doi Inthanon in 2014. Only points linking data from elevation zones 2,000–2,500 m and>2,500 m are connected by lines. Equitability declines profoundly at higher elevations between September and November indicating a decline in evenness of Diptera assemblages with corresponding prevalence of a number of relatively abundant species compared with other times of year and other elevations.

Fig. 5 in Spatiotemporal dynamics of insect diversity in tropical seasonal forests is linked to season and elevation, a case from northern Thailand

Fig. 5. Spatiotemporal variation in abundance and species richness of Diptera and Auchenorrhyncha trapped over 12 months sampling over six 500 m elevation zones at Doi Inthanon in 2014. The left panel shows Relative Abundance, A* (number of individuals caught. trap-1. month-1) as log (1+A*) for Diptera (A) and Auchenorryncha (C). The right panel shows observed species richness, S, for Diptera (B) 10 obs and Auchenorryncha (D). Data were plotted on a grid of elevation zone (vertical axis) and months (horizontal axis) and mapped using the multiquadric gridding algorithm in the gridding module of PAST. Values of log10(1+A*) and Sobs are indicated by the colour scale bars. Data are not available for January and February at <500 m and 500–1,000 m.

opencc-by-4.0Sep 2021View details →

Fig. 1 Insect alpha-diversity across tropical forest habitats. a in Mangroves are an overlooked hotspot of insect diversity despite low plant diversity

Fig. 1 Insect alpha-diversity across tropical forest habitats. a Mangroves treated as one habitat; b Comparison of mangrove sites: Pulau Ubin (PU), Sungei Buloh (SB), Pulau Semakau old-growth (SMO), Pulau Semakau new-growth (SMN), other smaller mangrove fragments (see Additional File 1: Table S13); solid lines = rarefaction; dotted = extrapolations. The arrow on the x-axis indicates the point of rarefaction where species richness comparisons were made (see bar charts for absolute numbers with 95% confidence intervals)

publicSep 2022View details →

Tropical–temperate comparisons in insect seed predation vary between study levels and years

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publicJan 2023View details →

Data from: Out of the tropics: Macroevolutionary size trends in an old insect order are shaped by temperature and predators

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opencc-zeroAug 2020View details →

Datasets - Evolutionary history, not ecogeographic rules, explains size variation of tropical insects along elevational gradients

One of the best-known biogeographic rules for ectotherms is the temperature-size rule, which asserts that ectotherms produce smaller adults at warmer temperatures. Although this is often true, it has become clear that there is no single process behind the pattern and many exceptions to the rule. To disentangle such complex temperature-size relationships, individual clades must be examined at ecological and evolutionary scales. We examined temperature-size relationships for 2106 individuals from 64 populations and 40 species of Cephaloleia rolled-leaf beetles (Chrysomelidae; Cassidinae) occurring along two tropical elevational gradientss: Barva and the Talamanca Cordillera in Costa Rica, Central America. We tested whether the temperature-size rule applied to interspecific elevational assemblages, intraspecific elevational populations, or different rearing temperatures for individual populations. At the interspecific scale, evolutionary history, rather than elevation, explains body size. At the intraspecific scale, only one of seven species followed the temperature-size rule across elevations. When larvae were reared at different temperatures, only one of five populations followed the temperature-size rule. Most populations grew to a fixed size regardless of temperature. Size in Cephaloleia beetles is constrained by their evolutionary history and responds to factors that rarely correlate with temperature. As temperature increases, ectotherms will not universally shrink, but determining if and why their size will change will require further investigation. Here we provide the following datasets used to determine effects of temperature on insect body size at population and community levels: Supplement S1. Body length for 2106 individuals representing 64 populations from 40 species of Cephaloleia rolled-leaf beetle along the Barva and Talamanca elevational gradients, Costa Rica. Supplement S2. Intraspecific differences in length for 798 individuals from seven Cephaloleia species present at multiple life zone. Supplement S3. Effects of developmental temperatures on Cephaloleia adult size in 968 individuals from four species and five populations reared in the laboratory at temperatures between 10 and 35 °C.

opencc-zeroDec 2017View details →

Data from: Vertical differentiation in tropical forest butterflies: a novel mechanism generating insect diversity?

Many tropical fruit-feeding nymphalid butterflies are associated with either the forest canopy or the understory, however, the exceptions offer insights into the origins of tropical diversity. As it occurs in both habitats of tropical forests in Ecuador and Peru, Archaeoprepona demophon is one such exception. We compared patterns of occurrence of A. demophon in the canopy and understory and population genomic variation for evidence of ecological and genetic differentiation between habitats. We found that butterfly occurrences in the canopy were largely uncorrelated with occurrences in the understory at both localities, indicating independent demographic patterns in the two habitats. We also documented modest, significant genome-level differentiation at both localities. Genetic differentiation between habitat types (approximately 20m in elevation) were comparable to levels of differentiation between sampling locations (approximately 1500km). We conclude that canopy and understory populations of A. demophon represent incipient independent evolutionary units. These findings support the hypothesis that divergence between canopy and understory-associated populations might be a mechanism generating insect diversity in the tropics.

opencc-zeroApr 2024View details →

Fruiting trees provide fruit and insect resources for four tropical deer species

Fruiting trees provide important fruit and seed resources for various animal species, but rarely are they considered to be rich sources of insects as well. During a study of seed dispersal of Trewia nudiflora (Euphorbiaceae) using camera-traps in Nepal, we observed four tropical deer species (Axis axis, Muntiacus vaginalis, Rusa unicolor, Axis porcinus) foraging for insects, rather than fruits under the trees. These herbivorous deer are proven seed dispersers of Trewia, but 8-38% of video captures (across each species) were of insectivory, rather than frugivory. The deer chased and consumed red cotton bugs (Dysdercus sp. family Pyrrhocoridae), which were seed predators that hoarded Trewia seeds. It is likely that other unidentified insect species were also consumed. Tropical deer species are considered to be fully herbivorous, so our observations extend their known diets and possibly indicate a seasonal requirement for protein. These findings also highlight tri-trophic interactions among deer, insects, and fruits that could have important implications for seedling recruitment if seed predators are being consumed by seed dispersers (in addition to fruit consumption).