Presence Of Extrafloral Nectaries Research Articles

Ant exclusion and reproduction of Croton sarcopetalus (Euphorbiaceae)

A total of 20 insect species were observed on the extrafloral nectaries (EFNs) of Croton sarcopetalus . The most frequent ant species were Zacryptocerus sp., Crematogaster brevispinosa, C. scelerata , and Linepithema humile . Ants continuously patrolled the plants taking extrafloral nectar. Experimental data showed that there were no significant differences in either the degree of herbivory or in the reproductive output between control stems (with ants) and treated ones (without ants). We found no significant evidence of protection by ants mediated by EFNs in C. sarcopetalus . It is possible that the plant has other mechanisms than ant protection to prevent herbivore damage (e.g., hairs, latex, chemical defense). As this species occupies the southernmost distribution for the genus, the presence of EFNs in this species may be the remnant of a mutualistic interaction with the ants in tropical regions, where the abundance and diversity of ants and herbivores are comparatively higher. To draw accurate patterns in the genus Croton , further investigations in other species from tropical regions of South America are needed.

Extrafloral nectaries in the tropical tree Guarea macrophylla (Meliaceae)

This paper describes the anatomy and morphology of the complex nectary systems of the tropical tree Guarea macrophylla Vahl (Meliaceae) and presents the first record of extrafloral nectaries occurring on reproductive organs (fruits) of a member of the order Sapindales. The extrafloral nectaries of G. macrophylla occur on petioles, petiolules, the abaxial surface of all leaflets, leaf buds, and over the surface of fruits. All extrafloral nectaries are distinctly raised above the surface. Foraging ants collect extrafloral nectar on Guarea trees both day and night. We suggest that the presence of extrafloral nectaries might be a useful taxonomic character for the identification of Guarea species. Key words: Guarea, Meliaceae, extrafloral nectaries, ants.

Ant-Homoptera Interaction: Do Alternative Sugar Sources Distract Tending Ants?

aggregations probably explains why ant tending levels remained unchanged in the presence of an alternate sugar source. The current experimental study and available field evidence from cerrado vegetation do not support the prediction that ants would neglect honeydew-producing homopterans in the presence of extrafloral nectaries.

Extrafloral Nectaries vs Ant-Homoptera Mutualisms: A Comment on Becerra and Venable

Becerra and Venable (1989) proposed that the function of extrafloral nectaries (EFNs) may not exclusively be to attract ants which defend plants against herbivores. They questioned the protection hypothesis and proposed that EFNs may also function to defend plants from ant-Homoptera mutualisms. Arguments for their hypothesis were e.g. the lacking universality of ant protection for plants and the negative impact of ant-tended homopterans on their host plants. In general, effects of homopterans on plants are negative but the damages of ant-homopteran associations are difficult to assess. Becerra and Venable cited a few examples of beneficial by-products of these associations in form of protection for the plants by the visiting ants. However, they considered only facultative interactions. In most of the highly developed ant-plant mutualisms ants cultivate homopterans while EFNs are absent. Among plant species of 36 genera, for example, which possess permanent domatia formed by hollow stems, only four have EFNs, but in 18 of them ants were recorded to keep homopterans (Huxley 1986). In the eight best-studied obligate myrmecophytic associations (Table 1) most plant partners offer nesting space but no food in form of nectar. The only two exceptions are Acacia spp. and Leonardoxa africana. In this respect the genus Macaranga (Euphorbiaceae) is especially interesting. In SE Asia it comprises the full range of species which are obligatorily inhabited by ants to those which have only weak and unspecific associations with ants (Fiala et al. 1989, 1990). Most of the facultatively associated Macaranga species possess EFNs on the leaf margins and in addition on the lamina. Obligate myrmecophytes in this genus do not secrete sugar-containing fluids (Fiala and Maschwitz, in press) and colonizing ants keep scale insects inside the hollow stems of their Macaranga host plants. Contrary to Becerra's and Venable's hypothesis in this case a reduction of nectary production appears to be favoured. The hypothesis of superiority of extrafloral nectar to honeydew remains to be tested in facultative associations, but my preliminary observations in Malaysia do not support this view. Becerra and Venable list a number of questions which should be addressed experimentally. I will briefly comment here on the first one: Is it generally true that ants neglect Homoptera when an alternative sugar source is available? During studies on the tree genus Macaranga in Peninsular Malaysia I looked for plants with EFNs and the occurrence of homopterans on these plants. The main study sites were secondary forests and disturbed habitat which were rich in light-demanding, fast growing plants. Six common species which possess EFNs were studied: Macaranga gigantea, M. tanarius, Mallotus paniculatus, M. macrostachys, Endospermum diadenum and Croton argyratus (all Euphorbiaceae). I checked 10 specimens each for occurrence of homopterans. Two to five plants of each species were infested by Homoptera (mostly scales and membracids) despite the presence of EFNs. Other plant species without EFNs in the vicinity were not found with homopterans more often than the above mentioned species (random samples of up to five nearest neighbouring plants; giving a total of over 200 controls). All homopterans on leaves and stems of the plants were visited by various ant species (Anaplolepis longipes and three Crematogaster spp. were dominant). The ants also visited the extrafloral nectaries on these plants. However, often the ants seemed to prefer honeydew from the homopterans. On a leaf of Croton argyratus, for example, almost 2/3 of all ants visited the scale insects on the leaf lamina and only few took notice of the secreted extrafloral nectar. On Mallotus ants generally favoured membracids despite

Nest Tree Selectivity by the Tropical Ant, Paraponera clavata

Nest Tree Selectivity by the Tropical Ant, Paraponera clavata

Extrafloral Nectaries on Plants in Communities without Ants: Hawaii

Since the Hawaiian Islands lack native ants, it was hypothesized that extrafloral nectaries, an ant-related mutualistic trait, should be lacking on native species. Presence of extrafloral nectaries (EFNs) on plants was determined by direct observation and related to vegetation structure and floral composition. Frequency of plants with EFNs was low by all possible comparisons. However, several endemic species had functional EFNs. The hypotheses to explain these anomalies are (1) phylogenetic inertia or (2) mutualism with some other organism than ants.

Distribution of Plants with Extrofloral Nectaries and Ants at Two Elevations in Jamaica

Frequencies of plants with extrafloral nectaries were determined for two elevations in Jamaica. Extrafloral nectaries were found on 0.28 of the plants at sea level (Happy Grove, Portland) and 0.00 of the plants at 1310 m (Whitfield Hall, St. Thomas). Ant abundance, as indicated by discovery of and recruitment to baits, was greater at the lower elevation site. However, despite the apparent absence of plants with extrafloral nectaries, there were abundant ants at 1310 m. MUCH EVIDENCE suggests that extrafloral nectaries attract insects which defend plants against herbivores and/or seed predators (Elias and Gelband 1975; Bentley 1976, 1977a, b; Keeler 1977). Extrafloral nectaries are glands which are located anywhere on a plant except those sites involved in pollination. These glands produce an aqueous solution containing sugars and other compounds (Baker and Baker 1975, Bentley 1977a, Keeler 1977). At present, only Bentley (1976) has studied the distribution of extrafloral nectaries in a natural habitat. She reported a positive correlation between frequency of plants with extrafloral nectaries and ant abundance in tropical dry forest in Guanacaste, Costa Rica. I report extrafloral nectary frequency and ant abundance from two sites in Jamaica. Two sites were compared: Happy Grove, Portland, Jamaica (sea level, approximately 1700 mm annual rainfall, mean annual temperature 260C, mean monthly temperatures 24-28?), and Whitfield Hall, near Hagley Gap, St. Thomas (1310 m up Blue Mountain, 3500 mm annual rainfall, mean annual temperature 220 C, mean monthly temperatures 16-32?). Since there are no weather records for the specific sites, values are extrapolated from U.S. Weather Bureau (1966) and Clarke (1974). Significant human disturbance was seen at both sites. Studies were conducted close to trails used daily by local people. The transects at both sites ran from under the forest canopy (presumably second growth) out into partially open areas (early second growth at Happy Grove, coffee fields at Whitfield Hall). Frequency of plants with extrafloral nectaries was determined in four transects at each site. At approximately every meter along each transect, plants were scored as having or lacking extrafloral nectaries and ants. The presence of extrafloral nectaries was determined by observing ants feeding in a stereotyped manner, and then locating the nectary. Once a species was determined to have extrafloral nectaries, it was scored as such on subsequent encounters. Ants were present at most extrafloral nectaries; of the 70 plants with extrafloral nectaries observed, only 10 (14%) did not have ants on them. The frequency of plants with extrafloral nectaries determined by this method is an underestimate, since some species may produce extrafloral nectar at other times of the year (e.g., fruit nectaries). Ant abundances were estimated by using baits of canned corned beef and local commercial jelly. A pile of each food about 1 cm in diameter was placed on a separate piece of plastic, 25 cm2, in the litter at each station. Time until arrival of the first ant, type of ant, peak number of ants responding and number of ant species attracted were recorded at each bait. Representative ants from baits at both sites and from foliar nectaries of plants at Happy Grove were collected. The experiments were carried out for three hours each, from 09.00-12.00 hrs in December 1977. Results from the extrafloral nectary transects are given in table 1. No species with extrafloral nectaries was observed at Whitfield Hall. At Happy Grove, 28 percent of the observed plants had extrafloral nectaries. These differences are statistically significant (T-test; p p> 0.01 and p-0.005, respectively). Ants collected from baits at Hatpy Grove included Paratrechina longicornis (Latreille), Solenopsis sp. 152 BIOTROPICA 11 (2): 152-154 1979 This content downloaded from 207.46.13.75 on Fri, 08 Jul 2016 05:47:31 UTC All use subject to http://about.jstor.org/terms (not S. geminata) , and Tetramorium guineense (F.); ants collected at Whitfield Hall were P. longicornis, Crematogaster brevispinosa Mayr., and Monomorium floricola (Jerdon). Ants collected from extrafloral nectaries at Happy Grove were P. longicornis, Solenopsis sp. (same as above), and Wassmannia auro-