Frugivorous weevils are too rare to cause Janzen–Connell effects in New Guinea lowland rain forest

Abstract

A community of frugivorous weevils was studied by quantitative rearing of 57 weevil species represented by 10 485 individuals from 326 woody plant species in lowland rain forest in Papua New Guinea. Only fruits from 35% of plant species were attacked by weevils. On average, weevils were reared from only 1 in 33 fruits and 1 kg of fruit was attacked by 2.51 individuals. Weevil host specificity was relatively high: 42% of weevil species fed on a single plant genus, 19% on a single plant family and only 16% were reared from more than one family. However, monophagous specialists represented only 23% of all reared individuals. The average 1 kg of fruits was infested by 1.84 individuals of generalist weevils (feeding on allogeneric or allofamilial host species), 0.52 individual of specialists (feeding on a single or several congeneric species), and 0.15 individual of unknown host specificity. Large-seeded fruits with thin mesocarp tended to host specialist species whereas those with thick, fleshy mesocarp were often infested with both specialists and generalists. Weevils tended to avoid small-seeded, fleshy fruits. The low incidence of seed damage (3% of seeds) suggests that weevils are unlikely to play a major role in regulating plant populations via density-dependent mortality processes outlined by the Janzen-Connell hypothesis.

A highly resolved food web for insect seed predators in a species‐rich tropical forest

“…Host specificity was consistently high across insect orders. This contrasts with results from studies on fruit-associated insects in Papua New Guinea (Ctvrtecka et al 2014;Sam et al 2017), where Curculionidae showed higher levels of specialisation than Lepidoptera. A possible explanation for the discrepancies in results between the two sites might be our more explicit focus on seed-eating insects (i.e.…”

Possible New Species of Araecerus (Coleoptera: Anthribidae) Associated with Mastixiodendron pachyclados (Garo garo), Rubiaceae

“…Further analysis using DNA barcoding technologies can confirm these species. Although Ctvrtecka et al [14] reared some Anthribid beetles also in Wanang Area, these remain unsorted therefore comparison cannot be done at the moment.…”

“…Ctvrtecka et al [14] obtained 1200 specimens of Anthribidae as a part of Curculionoidea in the same location, but they could not be reliably identified to species. Seven species were found but had to be excluded also because most of the specimens remain unsorted [14].…”

“…Ctvrtecka et al [14] obtained 1200 specimens of Anthribidae as a part of Curculionoidea in the same location, but they could not be reliably identified to species. Seven species were found but had to be excluded also because most of the specimens remain unsorted [14]. Morimoto [15] described Araecerus Schoenherr as having tarsal segment 3 bilobed, nearly as broad as segment 2; tarsi slender, segments 1 and 2 much longer than wide; front tibiae simple at least in female; front tarsi normal; lateral prothoracic carinae reaching the middle; front tarsal segment 1 longer than the remaining segments added together; and eyes oval, less prominent.…”

The insect‐focused classification of fruit syndromes in tropical rain forests: An inter‐continental comparison

“…Our previous analyses identified fleshiness as a critical trait for insect frugivores and seed predators (Ctvrtecka, Sam, Brus, Weiblen, & Novotny, ). The proposed entomology fruit classification system recognizes fleshiness as an important criterion, as does the botany system.…”