Seasonality in light‐attracted chrysomelid populations in a Bornean rainforest

Abstract

1. Seasonal or annual population fluctuations have been reported for various tropical insect species, exhibiting one or more peaks in abundance at certain times of the year. Such fluctuations have mostly been observed in areas that experience annual wet and dry seasons, and not in areas where climatic fluctuations are unpredictable on an annual basis.2. This study attempted to evaluate the extent of seasonality in population fluctuations of a light-trapped chrysomelid assemblage consisting of 25 Garelucinae and one Eumolpinae in a Bornean rainforest that is characterised by an aseasonal climate.3. This study also attempted to test the effects of short-term rainfall changes and leaf-flushing phenology on chrysomelid population fluctuations.4. The majority of the chrysomelid species showed one or more abundance peaks that were unrelated to season.5. The population fluctuations did not correspond to short-term fluctuations in rainfall or leaf-flushing phenology, although these environmental factors somewhat correlated with each other and fluctuated irregularly.6. These results suggest that populations of most chrysomelids fluctuate aseasonally and that short-term fluctuations in rainfall and leaf-flushing phenology hardly affect population fluctuations in Bornean rainforests where seasonal climate patterns are weak.

Tropical phenology: bi‐annual rhythms and interannual variation in an Afrotropical butterfly assemblage

“…To our knowledge, none of the long-term studies have studied correlations between plant phenology and temporal dynamics of tropical insect communities. Among the shortterm studies, no correlation was found between leaf beetle population fluctuations and leaf-flushing phenology in Borneo (Kishimoto-Yamada et al 2010), while the abundance of geometroid moths in Malaysia correlated positively with amount of flowering and leaf-flushing in the previous month (Intachat et al 2001). In addition to seasonal changes, natural populations of short lived organisms also experience annual fluctuations in their abundance, and therefore, tropical insect communities can be expected to change at inter-annual time scales as well.…”

Wide Host Ranges of Herbivorous Beetles? Insights from DNA Bar Coding

“…From 1994–1997, the proportion of flushing trees, defined as trees with more than 10% of all crown leaves in the newly developing or immature stages, ranged from 3.8 to 30.1% [23], and flushing trees increased irregularly as 14- and 30-day cumulative rainfall decreased [22,23]. In addition, a number of community-wide synchronous flowering periods, defined as periods during which more than 6% of individual canopy trees undergo flowering, occurred irregularly at intervals of several years, and the number of flowering trees approached zero during non-flowering periods [21,42].…”

“…The beetle specimens used for DNA extraction were mounted as voucher specimens and are maintained at Forest Research Centre. The chrysomelids were discriminated into morphospecies and identified on the basis of external characteristics, with reference to a collection of specimens used for previous studies [23,24]. …”

“…Previous studies have demonstrated that many herbivores prefer young leaves and flowers over mature leaves in the tropical forest canopy (e.g., [17–20]). The leaf and flower production of many dipterocarp trees is known to fluctuate synchronously among species at irregular intervals [13, 14, 21–23]. In contrast, the adults of some leaf chewer species emerge constantly throughout the year and fluctuate in abundance independently of dipterocarp tree phenology [23,24], although they have been observed to feed on the young leaves and flowers of dipterocarp trees [25].…”

“…The leaf and flower production of many dipterocarp trees is known to fluctuate synchronously among species at irregular intervals [13, 14, 21–23]. In contrast, the adults of some leaf chewer species emerge constantly throughout the year and fluctuate in abundance independently of dipterocarp tree phenology [23,24], although they have been observed to feed on the young leaves and flowers of dipterocarp trees [25]. This pattern leads us to hypothesize that these leaf chewer species are able to feed on other plant species when the young leaves and flowers of dipterocarp trees are unavailable.…”