Phenological synchrony and seasonality of tree species in a fragmented landscape in the Colombian Andes

Introduction: In Neotropical forests with high seasonality, climatic variables generally exert a strong influence on plant phenology. Objetive: To describe the reproductive phenology of eight tree species in a fragmented forest landscape, as well as to evaluate the seasonality and their phenological synchrony. Methods: The observations were performed over two years on the foothills of Los Farallones de Cali National Park, in southwestern Colombia. We applied circular statistics to detect seasonal trends, calculate intraspecific synchrony and identify correlations between phenophases and climatic variables. Results: Flowering and fruiting were significantly seasonal in most species. The flowering and fruiting patterns were annual (e.g. Henriettea seemannii, Ocotea aurantiodora, Schefflera morototoni, Lacistema aggregatum) or sub-annual (e.g. Eugenia cf. egensis, Erythroxylum citrifolium, Miconia minutiflora, M. rubiginosa). The open flower and mature fruit phenophases at the community level were continual and bimodal. Each species had high intraspecific population synchrony of open flowers and ripe fruits. Precipitation, relative humidity, temperature and solar irradiance were correlated to flowering and fruiting peaks, except in E. cf. egensis. Conclusions: The annual species showed high phenological synchrony, although the rainfall regime showed variations between years; thus, they seem to be less sensitive to climatic variation than the sub-annual species. Our results indicate that climatic variables partially control the flowering and fruiting rhythms of the eight tree species in this study.

Misunderstanding mismatch

This is a reponse to Kharouba and Wolkovich's (2020) review of consumer-resource phenological synchrony. They provide a valuable review and cogent advocacy for future work. However, they misunderstand and misinterpret examples from plant-insect interactions. Their detailed case study involves phenological synchrony/ asynchrony between spring hatching of Winter Moth eggs and budburst of their oak hosts. Published studies of this and other insect/plant systems are misinterpreted by applying a definition of phenological synchrony as "the situation in which the most energetically demanding period of the consumer's life cycle overlaps with the period of resource availability." This definition works well for ornithologists, since parent birds require high caterpillar abundance when their chicks are most demanding. But for Winter Moth the crucial phenological event occurs when larvae are just hatched and least demanding of energy, not most demanding (see below). The important role of phenological synchrony in most insect-plant systems is to fit the life cycle into the available time, not to synchronize peak resource demand with peak availability. The same is true of the Bay Checkerspot butterfly, for which baseline data are available from 1968-71 and 1983-5, showing that a fecundity-mortality tradeoff generated a persistent, adaptive, phenological asynchrony between the insect and its hosts, killing 70-80% of larvae each year.Kharouba HM, Wolkovich EM. 2020. Disconnects between ecological theory and data in phenological mismatch research. Nat Clim Chang 10: 406-415

Bumble bees damage plant leaves and accelerate flower production when pollen is scarce

Maintaining phenological synchrony with flowers is a key ecological challenge for pollinators that may be exacerbated by ongoing environmental change. Here, we show that bumble bee workers facing pollen scarcity damage leaves of flowerless plants and thereby accelerate flower production. Laboratory studies revealed that leaf-damaging behavior is strongly influenced by pollen availability and that bee-damaged plants flower significantly earlier than undamaged or mechanically damaged controls. Subsequent outdoor experiments showed that the intensity of damage inflicted varies with local flower availability; furthermore, workers from wild colonies of two additional bumble bee species were also observed to damage plant leaves. These findings elucidate a feature of bumble bee worker behavior that can influence the local availability of floral resources.

Phenological synchrony shapes pathology in host–parasite systems

A key challenge surrounding ongoing climate shifts is to identify how they alter species interactions, including those between hosts and parasites. Because transmission often occurs during critical time windows, shifts in the phenology of either taxa can alter the likelihood of interaction or the resulting pathology. We quantified how phenological synchrony between vulnerable stages of an amphibian host ( Pseudacris regilla ) and infection by a pathogenic trematode ( Ribeiroia ondatrae ) determined infection prevalence, parasite load and host pathology. By tracking hosts and parasite infection throughout development between low- and high-elevation regions (San Francisco Bay Area and the Southern Cascades (Mt Lassen)), we found that when phenological synchrony was high (Bay Area), each established parasite incurred a 33% higher probability of causing severe limb malformations relative to areas with less synchrony (Mt Lassen). As a result, hosts in the Bay Area had up to a 50% higher risk of pathology even while controlling for the mean infection load. Our results indicate that host–parasite interactions and the resulting pathology were the joint product of infection load and phenological synchrony, highlighting the sensitivity of disease outcomes to forecasted shifts in climate.