Interactions between ants and non-myrmecochorous diaspores in a West African montane landscape

Myrmecochory, the dispersal of seeds with lipid-rich appendages by ants, is a significant ant–plant interaction. Less well understood is the potential for ant dispersal of non-myrmecochorous seeds. Here we investigate ant–diaspore interactions in a West African montane habitat. We combine observation with depot experiments to determine ant species that move diaspores and distance moved across a forest-edge-grassland gradient. We recorded seed cleaning by ants using a bird/mammal dispersed Paullinia pinnata to determine whether seed cleaning improved plant fitness. We found that two out of a total of 17 ant species (Pheidole sp. 1 and Myrmicaria opaciventris) interacted with 10 species of non-myrmecochorous diaspores across nine plant families. Diaspores were from large canopy trees, understorey trees and vines. Both ant species interacted with small (≤0.24 g) and large (≥0.24 g) diaspores. Ants individually moved small diaspores up to 1.2 m and worked together to clean larger ones. Our experiments with P. pinnata showed that ants removed the pulp of 70% of fruit over 5 days. Cleaned seeds germinated significantly faster and produced seedlings with significantly longer shoot length and higher fresh weight than seedlings from intact seeds. Together our results suggest that ant dispersal may be less significant than seed cleaning in Afromontane forests. However, given the decline in vertebrate frugivores across Africa, a small dispersal advantage may become increasingly important to plant fitness.

Typification of the Linnaean name Empetrum album (Ericaceae)

The genus Corema D. Don (1826: 63) (Ericaceae Jussieu 1789: 159) comprises two species. Corema album (Linnaeus 1753: 1022) D. Don (1830: 460) (incl. C. febrifugum Boissier ex Willkomm & Lange 1877: 512) occurs on the west coast of the Iberian Peninsula (subsp. album) from Gibraltar to Finisterre (Willkomm & Lange 1877, Webb 1972, Cabezudo 1987, Villar 1993, Boratyński & Vera de la Puente 1994, López González 2001, Ruiz de la Torre 2006, Gil-López 2011), the Azores (subsp. azoricum Pinto da Silva 1966: 86), and the Mediterranean Basin (Spain, Alicante province, one population) (Solanas 1996, Solanas & Crespo 2001, Serra 2007, Aguilella et al. 2009). Corema conradii (Torrey 1837: 83) Torrey (1842: 1092) occurs on the eastern coast of North America from Newfoundland to New Jersey (Redfield 1884, McEwen 1894, Elisens 2009), and can be distinguished from C. album by its very small fruits which are devoid of fleshiness and covered with elaiosomes (oily appendages associated with ant dispersal) (Redfield 1884, McEwen 1894, Martine et al. 2005). Corema album subsp. azoricum exists on six of the nine islands of the Azores, and below 200 m (Franco 1984) this taxon has been recognized by some authors at the species level as C. azoricum [“azorica”] (Pinto da Silva 1966) Rivas Martínez, Lousã, Fernández Prieto, E. Días, J.C. Costa & C. Aguiar (in Rivas-Martínez, Fernández-González, Loidi, Lousã & Penas 2002: 700).

Pollen and reproductive morphology of Rhigiophyllum and Siphocodo (Campanulaceae): two unique genera of the fynbos vegetation of South Africa

Pollen grains of Rhigiophyllum squarrosum Hochst., Siphocodon spartioides Turcz. and S. debilis Schltr., are flattened and triangular with pores at the angles. This morphology is radically different from known pollen of the Campanulaceae s.sfr:: the Campanulaceae are treated here as a family separate from the Lobeliaceae, Cyphiaceae, Nemacladaceae, Pentaphragmataceae and Sphenocleaceae (Lammers 1992). As traditionally conceived, the Campanulaceae is very heterogeneous and, in many classifications, these families were treated as subfamilies of a much-enlarged Campanulaceae. The consistently different floral morphology, biochemistry and pollen structure of the Lobeliaceae favours the recognition of this predominantly tropical group as a separate family.The pollen grains of these species are described in comparison with other members of the Campanulaceae. Based on surface characteristics of their pollen grains, we conclude that they represent an early offshoot o f the wahlenbergioid line­age in southern Africa. We suggest that this unique pollen may also be the result of a highly selective regime in the fynbos, associated with specialized pollinators, and base-poor soils, in addition to possible adaptations for ant dispersal and fire. Rhigiophyllum Hochst. and Siphocodon Turcz. are also unique in having free carpel-like structures within the ovary. These shrink to form seed pockets around the seeds and disperse as units when the capsule matures. Data from molecular studies support the contention that these taxa form a sister group to all other wahlenbergioids and that this should be formally recognized in a classification system. We treat Rhigiophyllum and Siphocodon within the Campanulaceae: Wahlenbergioideae, as a separate tribe, the Rhigiophylleae tribus nov., the species of which are distinguishable from other wahlenbergioids by unique angulaperturatc pollen, epipetalous stamens, free carpel-like structures and seed pockets.

Do generalisations of global trade-offs in plant design apply to an Australian sclerophyllous flora?

Functional-trait analysis at a global scale has found evidence for evolutionary specialisation of species into those designed to acquire resources rapidly and those designed to conserve resources. The present study aimed to determine whether such a trade-off exists in sclerophyllous vegetation in Australia. We measured 10 traits for 167 plant species. The first axis of a principal components analysis represented a trade-off between resource acquisition and resource conservation, consistent with global trends. Common traits shared by resource-conservative species included low specific leaf area (SLA), resprouting, ant-dispersal, and ericoid mycorrhizal and ectomycorrhizal associations. These attributes were typical of 3 of 13 functional groups produced by cluster analysis (eucalypts, ant-dispersed shrubs, ericoid heaths) that had the lowest SLA, and were almost exclusively native shrubs and trees. Resource-acquisitive species had high SLA, a small stature, annual life cycle, arbuscular mycorrhizal or non-mycorrhizal associations, and small, wind-dispersed seeds. These attributes are similar to those identified for species with a ruderal strategy and were typical of the functional groups representing wind-dispersed composites, AM annuals and non-mycorrhizal annuals that had the highest SLA and were dominated by introduced species. Comparable trait associations have been found in other studies, suggesting that similar processes drive plant design at a global scale. However, there were some patterns specific to the flora studied that were attributable to adaptations to suit the nutrient-poor soils and arid conditions typical of the Australian environment.

Myrmecochory in the Zingiberaceae: seed removal of Globba franciscii and G. propinqua by ants (Hymenoptera – Formicidae) in rain forests on Borneo

The Old-World tropics encompass one of the floristically richest zones of the world and some of the hot spots of ant diversity. This results in a large variety of ecological interactions between both groups. One of them is the phenomenon of myrmecochory, seed dispersal by ants, which is also well known from temperate forests (Gorb & Gorb 2003, Ulbrich 1919), and which is most prominent in sclerophyll shrublands of Australia and southern Africa (Andersen 1988). Beattie (1983), who reviewed the distribution of ant-dispersed plants (at least 80 plant families worldwide) proposed that species richness and abundance of myrmecochores and diaspore-dispersing ants increases with decreasing latitude and thus predicted a greater variety of ant-dispersal systems in the tropics. However, up to now, few tropical myrmecochores have been described (Horvitz 1981, Horvitz & Schemske 1986), especially in the palaeotropics (Kaufmann et al. 2001). Here we report myrmecochory in two species of rain-forest herb of the Zingiberaceae, give the first evidence for seed dispersal by ants in this plant family and present a list of seed-dispersing ant species. An important benefit of myrmecochory is the dispersal distance of the ant-transported seeds (Andersen 1988), that has been found to be positively correlated with ant size (Gomez & Espadaler 1998a, Pudlo et al. 1980). In this study, we checked whether this correlation is also true for the conditions of the tropical rain forest, where Globba plants occur.