Environmental control of flowering periodicity in Costa Rican and Mexican tropical dry forests

Abstract

Aim We analyse the proximate causes of the large variation in flowering periodicity among four tropical dry forests (TDF) and ask whether climatic periodicity or biotic interactions are the ultimate causes of flowering periodicity.Location The four TDFs in Guanacaste (Costa Rica), Yucatan, Jalisco and Sonora (Mexico) are characterized by a 5 -7 month long dry season and are located along a gradient of increasing latitude (10 -30 ° N). MethodsTo dissect the differences in flowering periodicity observed at the community level, individual tree species were assigned to 'flowering types' , i.e. groups of species with characteristic flowering periods determined by similar combinations of environmental flowering cues and vegetative phenology. ResultsLarge variation in the fraction of species and flowering types blooming during the dry and wet season, respectively, indicates large differences in the severity of seasonal drought among the four forests. In the dry upland forests of Jalisco, flowering of leafless trees remains suppressed during severe seasonal drought and is triggered by the first rains of the wet season. In the other forests, leaf shedding, exceptional rainfall or increasing daylength cause flowering of many deciduous species at various times during the dry season, well before the summer rains. The fraction of deciduous species leafing out during the summer rains and flowering when leafless during the dry season is largest in the Sonoran TDF. Main conclusionsIn many wide-ranging species the phenotypic plasticity of flowering periodicity is large. The distinct temporal separation of spring flowering on leafless shoots and subsequent summer flushing represents a unique adaptation of tree development to climates with a relatively short rainy season and a long dry season. Seasonal variation in rainfall and soil water availability apparently constitutes not only the proximate, but also the ultimate cause of flowering periodicity, which is unlikely to have evolved in response to biotic adaptive pressures.

Continental-scale patterns of Cecropia reproductive phenology: evidence from herbarium specimens

“…This result supports the many studies that have shown strong associations between flowering, precipitation and temperature patterns [6,7,9]. Although our results indicate that climate seasonality is associated with Cecropia phenology, determining the individual roles of temperature and precipitation was not possible in this observational study.…”

“…Correlative approaches have frequently shown phenological parameters to change in concert with environmental variables. Variation in precipitation, soil water availability, temperature, irradiance and day length seem to control the periodicity of flowering and leaf abscission in many tropical species [3][4][5][6][7]. Understanding the links between phenological patterns and environmental variables is crucial to advance the study of community and species dynamics under various climate change scenarios.…”

Diversity of deciduousness and phenological traits of key Indian dry tropical forest trees

“…In few species vegetative buds break during June (after the first significant rain of rainy season) indicates the predominant role of rains in leaf flushing. Rapid rehydration due to rains results in synchronous buds break in trees (Borchert et al, 2004). Occurrence of leaf flushing during the dry season (well before the onset of rainy season) in leaf-exchanging and majority of deciduous species may also be an adaptation to reduce the herbivorous insect attack.…”

Flowering and fruiting phenology in maquis of New Caledonia

“…An immediate classification would consist in separating annual flowering species from others. Another one, suggested by Borchert et al (2004), consist in classifying the species according to the period of the flowering (i.e. summer, autumn and winter species).…”