Phenological Separation Research Articles

Phenology of the shrub strata of successional sub-tropical humid forests of north-eastern India

The phenology of 70 shrub species occurring in 5-, 25- and 60-yr old forest fallows, developed after slash and burn agriculture in north-eastern India, was studied. The early successional shrubs were largely deciduous with predominant leaf fall during the dry winter, while late successional shrubs were evergreen and with a less pronounced leaf fall pattern; the species in the 25-yr old fallow were largely of the leaf-exchanging-evergreen type. Peak leaf production, flowering and fruiting are delayed by one month in the 60-yr old fallow. The phenological separation of the growth types in the three fallows is discussed and related to possible micro-environmental differences.

Floral Biology and Pollination Ecology of the Neotropical Species of Parkia

(1) The floral biology and pollination ecology of eleven species of the pantropical genus Parkia (Leguminosae: Mimosoideae) were studied in Amazonian Brazil. Most are large forest trees. (2) The unit of pollination is a ball-like capitulum composed of many small flowers. Specialized flower types are arranged in different ways in the three taxonomic sections of the genus and this has important implications for pollination. (3) Nine species in two sections are bat-pollinated. Their floral adaptations and the mechanism of pollen transfer are similar although there are many differences in details. Individual capitula open for one night, secrete copious nectar, have distinctive smells, are bright red, or yellow, or both, and are held beyond the foliage or rarely within the crown. (4) Andromonoecy occurs in most species; several have a proportion of their capitula with all the fertile flowers functionally male, probably indicating a mechanical constraint on fruit production. Some species appear to be protandrous. (5) Eight species of bats from four subfamilies of the Phyllostomidae were caught at flowering trees. The most important pollinator is Phyllostomus discolor. Bats acting as pollinators land briefly on capitula to take pollen and nectar. In some species, a landing platform is provided by the basal fringe of elongated staminodial filaments. Some small bats take nectar on the wing without contacting the fertile flowers and thus act as nectar thieves, (6) Sympatric chiropterophilous species reduce competition for pollinators primarily by phenological separation. Different flowering strategies affect the range of bat species attracted. Vision is apparently important in the location of open capitula. (7) Non-flying mammals, hummingbirds, bees, wasps, moths, and other insects take nectar or pollen or both but none is likely to be important in the pollination of the chiropterophilous species. (8) Comparison with the pollination of Parkia by pteropodid bats in the palaeotropics emphasizes the similarities in many features. The principal difference is in the landing position of the bat. (9) One taxonomic section, whose capitula lack specialized nectar-secreting flowers, is wholly or partly entomophilous, and visited especially by trigonid bees.

Increased or Decreased Separation of Flowering Times? The Joint Effect of Competition for Space and Pollination in Plants

In earlier reports the effect of an increased temporal segregation of flowering times of co-occurring species has been considered to lead either to increased seed production through decreased competition for pollination and/or pollinators, or to decreased competition between seedlings. However, these two processes are negatively coupled in that increased seed production will lead to increased competition between seedlings. In this article we analyse the consequences of this in a two-species model. We show that there are three possible results of an increase in phenological separation: (1) both species gain fitness; (2) species 1 gains and species 2 loses fitness; and (3) species 1 loses and species 2 gains fitness. We discuss how these results depend upon strength of the coupling between a change in phonological separation and the change in seed production.