Shared pollinators and sequential flowering phenologies in two sympatric cactus species

Background and aims – The reproductive characteristics of sympatric Cactaceae are important because they help to understand interfering or facilitating mechanisms that allow their coexistence. Globose Cactaceae show melittophily flowers that may be attractive to a shared set of pollinators, and if the flowering events are not overlapping, flower resources could be present for the pollinators through time. Ariocarpus kotschoubeyanus and Neolloydia conoidea are two sympatric cactus species in the southern Chihuahuan Desert. The objective of this study is to describe and compare some reproductive characteristics of these species.Material and methods – Individuals of Ariocarpus kotschoubeyanus and Neolloydia conoidea (n = 231 and 212, respectively) were marked and monitored during one year, recording for each species, the floral phenology, behaviour and morphology, flower visitors, breeding and mating systems (through pollination experiments).Key results – The flowering periods of these species do not overlap. The flowers of both species are melittophily, with the same shape, colour, and similar behaviour; both are obligate xenogamous plants. The mating system of Neolloydia conoidea is outcrossing but mixed in Ariocarpus kotschoubeyanus. They share 75% of pollinators (solitary and social bees).Conclusions – The temporal blooming separation of these species could be an important factor to facilitate coexistence within the xerophyte community since they share the same set of pollinators to achieve their reproductive success.

Phenology of two co-occurring Piper (Piperaceae) species in Brazil

The co-occurrence of some species, including members of the Piper genus, has been shown to be associated with phenological factors. In the present study we analysed vegetative (sprout production and leaf flush) and reproductive phenophases (spike production, flowering, spike abortion, fruiting and dispersed spikes) of the co-occurring species Piper gaudichaudianum Kunth and Piper vicosanum Yunck. and checked the influence of abiotic factors on their phenological behaviour. Our study addressed natural populations in a semi-deciduous seasonal forest in south-eastern Brazil. In both species, the phenophases occurred mainly in the rainy season, were seasonal and associated with environmental variables, especially day length. However, sequential flowering and fruiting isolated them temporally from each other. Other differences were the growth of sexually reproductive sprouts (45.7% of the total sprouts) and the production of latent spikes in P. vicosanum; in P. gaudichaudianum, only 7.1% of the sprouts produced spikes that were not latent. Spike abortion was high: 73.8% (n = 474) in P. vicosanum and 84.8% (n = 231) in P. gaudichaudianum. The remaining spikes with fruits dispersed, on average, 293 and 1168 seeds per spike respectively. Although annual phenological behaviour of the species is regulated by similar environmental variables, their distinct reproductive strategies seem to favour the maintenance of the co-occurring populations.

Sequential Flowering of Thistles (Cynareae, Asteraceae) in Southern Australia

Flowering patterns of four and seven species of thistles were examined in Wagga Wagga, N.S.W. and Canberra, A.C.T. respectively, during the 1982-83 and 1983-84 flowering seasons. Flowering patterns at each location were sequential, consistent and differed significantly among species. The progression of anthesis among the species was as follows: Carduus pycnocephalus, Silybum marianum, Onopordum acanthium, O. illyricum, Centaurea calcitrapa, Carthamus lanatus and Cirsium vulgare. Early-flowering species typically had brief flowering periods whereas later species flowered for con- siderably longer periods. Seed (achene) dormancy patterns and optimum temperatures for germination of the first and last species of the sequences were analysed. Seeds of C. pycnocephalus exhibited pro- nounced innate dormancy for at least 2 months after seed maturation and germinated poorly at high temperatures. In contrast, some seeds of C. vulgare were able to germinate soon after seed maturation and over a wide range of temperatures. Early-flowering species probably benefit from pronounced dormancy by avoiding precocious seed germination during wet springs, while high temperatures prob- ably restrict germination after rare rainfall during the long and dry summers of Mediterranean-like southern Australia. Such dormancy is unnecessary for late-flowering species in this environment as their seeds are produced coincidentally with the onset of more reliable autumn rains.

General flowering in the climax rain forests of South-east Asia

ABSTRACTThe general flowering of lowland dipterocarp forests of South-east Asia is a unique phenomenon that occurs intermittently, sometimes many years apart, and may be widespread throughout the region or sporadic. During a general flowering a very large number of tree families, including the well-known Dipterocarpaceae, flower and fruit exceptionally heavily. The huge pulse of flowering is echoed by an apparent explosion in the number of pollinators, and this is further augmented by migration of pollinators from the forest fringes. The huge demand for pollinators seems to be solved among several dipterocarps through utilization of tiny, fast breeding, floral-feeding insects such as thrips and hoppers. Competition for pollinators is further reduced through development of sequential flowering among several groups of trees that share similar pollinators. The resulting massive general fruiting seems to contribute to a heightened level of faunal activity and numbers. This long-intervalled flowering and fruiting phenology which dominates these lowland dipterocarp forests may have partly contributed to the lowered animal biomass frequently alluded to when these forests are compared with neotropical forests.