Freerk Molleman

Assessing the conservation value of secondary forests and reforestation is important for conservation planning. Butterflies are widely used as indicators, and fruit-feeding butterflies are often used in biodiversity assessments in tropical landscapes. We examined fruit-feeding butterfly diversity, abundance, and community composition across a primary forest, a secondary forest, and a plantation forest in northern Vietnam. We sampled butterflies nearly monthly during one year using baited traps. Primary and secondary forest supported higher species richness than plantation forest. Moreover, while secondary forest had mainly a subset of species found in primary forest, the plantation forest had a distinct butterfly fauna. Butterfly abundance and community composition varied across months, without showing a clear seasonal pattern. Our results suggest that secondary and plantation forests do not fully replace primary forests, but they contribute meaningfully to butterfly conservation in human-modified tropical landscapes.

Koinobiont parasitoids have been shown to both reduce and increase the growth rate of caterpillars. However, no comprehensive study has been conducted on several caterpillar hosts of a given plant species. Moreover, most of the existing case studies are on large caterpillars attacking crop plants. This may not be representative of the effect of parasitoids on the growth of caterpillars that feed on trees. We sampled caterpillar communities from the canopy of oak trees (Quercus robur and Q. petraea) in a forest in France and from one in Poland, measured their growth rate, and noted parasitoid exit. The details of the methods varied between study years and locations, and this was partially accounted for statistically. Across six species of Lepidoptera, parasitoids reduced caterpillar growth rate on average. The effect of parasitism appeared to vary widely within and across lepidopteran species, indicating diversity in the outcome of plant–herbivore–parasitoid interactions. Further studies should verify this result and determine if the reduced growth rate is accompanied by lower plant consumption rates. If so, plants would immediately benefit from attracting parasitoids when they are attacked by caterpillars, and forestry practices that increase parasitoid abundance could reduce folivory partly without delay.

Many tropical butterflies exhibit seasonal wing pattern plasticity, producing cryptic dry-season morphs with small or no ventral eyespots and conspicuous wet-season morphs with large wing-marginal eyespots that deflect predator attacks away from vital body parts. Eyespot size is influenced by temperature during larval development. However, many tropical regions lack a predictable temperature–rainfall correlation, limiting temperature’s reliability as a cue. Relative humidity (humidity), which increases with wet season’s approach, presents a potential environmental cue. We tested whether humidity modulates eyespot-size plasticity in two sympatric butterflies experiencing similar ecological pressures. High humidity directly induced larger eyespots in Mycalesis mineus, compared with those from low humidity. In contrast, Melanitis leda showed no direct effect; instead, humidity modulated eyespot size indirectly through induced changes in host plant quality. Since the late larval and prepupal stages are temporally closer to the adult environment, selection may favour greater sensitivity during these stages. Using a humidity switching experiment at different developmental stages, we demonstrated that, in M. mineus, wandering larval and prepupal stages are sensitive to humidity, while M. leda remained insensitive. This study highlights how two diverging species, evolving under similar ecological pressures, integrate environmental cues in distinct ways to modulate wing pattern plasticity.

In recent years, budburst, the timing of leaf emergence, has advanced less than expected despite continued spring warming, suggesting counteracting ecological forces. One of these forces might be increased and earlier herbivory on young leaves under climate warming. Here using 5 years of satellite radar data from 27,500 pixels (10 ×10 m ² ) across 60 temperate oak forest sites under experimental manipulation of insect herbivore loads in Central Europe, we show that prior-year leaf herbivory delayed budburst by 3 days, cancelling the phenological advance observed during a decade of warming. This delay reduced subsequent herbivory by 55%, exceeding the effects of parasitoids or pathogens, and persisted even during pest outbreaks. Across landscapes, the delay was strongest where it probably provided the highest benefit, that is, where a given amount of delay most effectively reduced following herbivory, which suggests an adaptive tree defence. Ultimately, trees may be trapped between responding to two opposing consequences of global change: warming selects for earlier budburst, whereas herbivory selects for delay. Our results underscore the need to consider not only climate, but also plant–herbivore interactions and adaptive evolution to predict tree responses to a changing world.

We report a long-read high-coverage reference genome assembly of the Neotropical butterfly, Batesia hypochlora (Nymphalidae: Biblidinae). This represents the first reference genome in the Biblidinae subfamily, a clade subject to ongoing studies on seasonal and climate adaptation in the Amazon. We assembled the genome from PacBio HiFi long reads (66X coverage), polished it with Illumina short reads (15X coverage), and annotated it using PacBio IsoSeq RNA data. We observed 15 chromosome-sized scaffolds, varying in length from 13.2 Mbp to 37.6 Mbp (median, 24.3 Mbp), which combined to form a total genome size of 395.788 Mbp. This assembly is highly contiguous (contig N50 of 25.14 Mbp) and complete (BUSCO completeness score of 98.6% and 0.2% duplication rate). Repeat annotation revealed that the genome comprises approximately one-third transposable elements. Gene prediction using RNA-seq evidence identified 19,395 genes, of which 17,400 were assigned to 2,883 orthogroups, including genomes of the fruit fly, silk moth, and three other Nymphalid butterfly species. The high sequencing depth also allowed us to assemble the genomes of the mitochondria and the common endosymbiotic bacterium Wolbachia . The mitochondrial genome was fully assembled (15,540 bp in size) with all expected genes annotated. The Wolbachia genome was fragmented, and we determined that it belongs to the B-supergroup. The high-quality assembly of B. hypochlora can represent the subfamily in further comparative analysis of evolution and provide a key resource for ongoing work to explore reproductive biology and adaptations to seasonality in Neotropical butterflies.

Herbivorous insects use both visual and chemical cues to locate suitable host plants in diverse vegetation. Because colour is among the most salient visual cues, such insects are expected to have preferences for particular colours when searching for host plants. To test whether colour preferences play a role during host‐plant selection, we performed a series of oviposition‐choice experiments on common evening brown butterflies ( Melanitis leda L.; Lepidoptera: Nymphalidae) using artificial grasses. This species uses a wide variety of grasses as host plants but nevertheless shows strong preferences among species of grass. We determined preferences between primary colours (red, blue and green), and preferences between greens that vary in (a) brightness (luminance), (b) hue (adding some blue or green) and (c) saturation (adding various amounts of grey). We found that these butterflies readily oviposited on artificial grass and responded to hue, brightness and saturation. They appeared to prefer bright green, pure green or slightly red‐shifted green, and green of high saturation. The acceptance of artificial grass shows that visual cues, possibly together with mechanical cues, can be enough to induce oviposition behaviour. The preferences appear to fit with the host‐plant use of this species. Our results highlight the importance of visual cues for ovipositing insects.

Inter‐annual variation in insect abundance and seasonal phenology can be related to species traits such as body size, larval diet, overwintering stage, and colour variation. We sampled noctuid moths in the canopy of a forest in Western Poland using flight‐interception traps during two vegetative seasons. We calculated inter‐annual variation for 31 species, and the date of peak abundance and length of the flight season for 18 species. We found that for the 23 species for which we had phylogenetic information, larger moths and those with adult colour variation showed less inter‐annual abundance variation, which corroborates the results of previous studies. We found no indication that phenological traits are associated with the tested species traits. However, species that can feed on the dominant broad‐leaved tree in which the traps were placed ( Quercus petraea ) tended to have a later date of peak abundance than other species. To draw more robust conclusions, future research should encompass a longer time span and a broader range of species.

For half a century, biologists considered trees as particularly apparent to their enemies. But why then do some trees escape herbivorous enemies by bursting buds either too early or too late, leading to phenological mismatch? We hypothesize that such mismatches occur on trees that are unapparent in time – those that burst buds ‘discreetly' (slowly) and unpredictably (inconsistently across years), and are difficult to access (host trees among non‐hosts). We studied herbivores on oaks in western France. We for the first‐time characterized phenology matching of an entire guild of herbivores, early spring ectophagous caterpillars (45 species). We examined whether, on a given date, caterpillars have a large body size and impact (herbivory), and whether this size or impact are largest on trees that burst buds earliest. Furthermore, we distinguished the contributions of within‐guild sorting of species and within‐population selection of individuals to phenology matching, we investigated whether present phenology matching was determined during past generations by testing if caterpillars from trees with early‐maturing foliage pupate early, even when transferred into a common garden. We found that caterpillar size and herbivory impact in the field and pupation date in the lab generally matched leaf phenology in the field. Such phenology matching was consistently observed at the intraspecific level but was less evident at the interspecific level. Together this indicates that phenology matching is mainly driven by past within‐population selection rather than present, within‐guild sorting. Furthermore, herbivores size and impact were most constrained by late bursting of host trees if these trees burst buds slowly and unpredictably and are difficult to access. We suggest that, during the assembly of early‐spring herbivore guilds, trees can best constrain development of herbivore populations by late budburst and remaining unapparent in time – bursting buds discreetly, unpredictably across years, or in inaccessible neighbourhoods.

Koinobiont parasitoids have been shown to both reduce and increase the growth rate of caterpillars. However, no comprehensive study has been conducted on all caterpillar hosts of a given plant species. Moreover, most of the existing case studies are on large caterpillars attacking crop plants. This may not be representative of the effect of parasitoids on caterpillar growth on trees. We measured the growth rate of parasitised and non-parasitised spring caterpillars collected from oak trees ( Quercus robur & Q. petraea ) in France and Poland. Across six species of Lepidoptera, parasitoids reduced caterpillar growth rate on average. Further studies should determine if the reduced growth rate is accompanied by lower consumption rates, so that the plant directly benefits from attracting parasitoids when they are attacked by caterpillars.