Ficus Species Found in American Samoa

Ficus is one of the largest plant genera of the tropics, which enjoys a cosmopolitan distribution. There are about 755 fig tree species worldwide, with around 511 of them occurring in the Indo-Australasian region (Asia, Malaysia, Pacific islands and Australia) and approximately 132 in the Neotropical region (Central and South America) (van Noort, Gardiner and Tolley, 2007). Ten species are native to Polynesia, but only six are found in American Samoa, which are aoa (Ficus prolixa), aoa (Ficus obliqua), mati (Ficus scabra), mati (Ficus uniauriculata), mati (Ficus godeffroyi), and mati (Ficus tinctoria) (Whistler, 2004).

Individuals of this genus, the "fig trees" as they are generally called are noted for their peculiar habit, varied diversity and strange relationship with small hymenopteran insects called fig wasps (van Noort & Compton 1988).

Cook (2003) reported that fig trees are considered one important food factor for monkeys, bats, and other animals. They play a crucial role in maintaining the populations and diversity of rainforest animals.

Ficus is identified as one of the 'keystone species' in many tropical and subtropical ecosystems, because of the all year round production of figs, providing food for a number of vertebrates and breeding place for invertebrates (Terbogh, 1986). A study in the African cities Komura, Mohyen-Chari, and Chad (Mandang area) showed that more than 440sp. of insect, 59sp. of birds and 17sp. of mammals directly depend on 15sp. of commonly occurring Ficus for their livelihood (Basset, Novotny, and Weiblen 1997). Pigeons, doves, and other frugivorous birds found in American Samoa feed on the fruits of the Ficus scabra and Ficus tinctoria (Whistler, 2004). In 2005, Utzurrum reported at least 42 plant species provide food for bats in American Samoa, which consist of two fig trees, F.prolixa and F.obliqua.

The fig insects can be generally classified into two categories, the pollinators and the non-pollinators. Fig trees are completely dependent on tiny wasps, a couple of millimeters long, for their breeding and survival (van Noort, 2004).

The necessity of the tiny wasps for good fruit set in cultivated figs was recognized over two thousand years ago by Aristotle and his pupil Theophrastus and the details of pollination in this species were understood by the early part of this century (Condit, 1950). There is much variability in fig inflorescence morphology, which is associated (by host specificity) with variability in fig wasp morphology (Ramirez, 1974) and behavior (Galil and Meiri, 1981). The fruits of all species of Ficus are colonized by a heterogeneous group of insects of the family Agaonidae. Ficus and these wasps breeding inside their ovaries, the 'fig insects' as they are commonly called, are figured as a classic example for obligatory mutualism and coevolution (van Noort, 2004).

These fig wasps are the sole pollinators of fig trees and in turn, fig wasps can breed nowhere else but inside figs, a relationship that is a classic example of an obligate mutualism (neither party can survive without the other) that has evolved over the last 60 or so million years (van Noort, 2004). Figs and their pollinator wasps are the most intricately coevolved of the plant-insect mutualisms (Ramirez 1970; Galil and Eisikowitch, 1970). Thus, the Ficus-fig insect relationship becomes a prime element in tropical ecosystem (Priyadarsana, 2000).

Besides the pollinators there is a suite of non-pollinating fig wasps that also breed in the fig, but which play no role in the pollination process (van Noort, 2004). From the fig's perspective they are unwanted interlopers (Bronstein, 1992). Most of the non-pollinators, however, lay eggs by inserting their ovipositor through the fig wall from the outside of the fig. Africa reports as many as 30 species of non-pollinating fig wasp can be associated with a particular fig tree species (van Noort, 2004).

Although Ficus play a remarkable role in the ecosystem functions of the tropics, no reports were found about fig wasps in American Samoa.

The objective of the present study was to identify fig wasps that are associated with various Ficus spp. found in American Samoa.

MATERIALS AND METHODS

I. Collection and Identification of fig trees

The search for fig trees was conducted in the villages of Fogagogo, Faleniu, Mapusaga, and Utulei, American Samoa. Hefty trash bags (83 cm x 96 cm) were used to obtain the fig branches, and Ziploc bags (17.7 cm x 19.6 cm) were used for the leaves. The resources obtained were then taken to ASCC Land Grant's customary lab for identification.

II. Collection and Preservation of Fig Wasps

Fig wasps were collected by placing fig fruits acquired from the fig trees stored in each of the 15 glass vials (straight-sided ½ oz. vial with cork). The fig fruits in the glass vials were kept for a minimum of 3 days in the Tafuna High School Science lab. Fig wasps that emerged from the fig fruits were shifted from the glass vials using a paintbrush to 75% ethanol for preservation.

III. Identification of fig wasps

Fig wasps (both males and females) were taken to the ASCC Land Grant entomology lab for identification. The fig wasps and fig fruits were randomly selected from 75% ethanol to be observed through a Nikon SMZ1500 stereomicroscope. A Nikon Digital Sight DS-Fi1 camera was used to capture photographs of the two resources being collected. The identification of the resulted fig wasps was verified by Boucek (1999) and with the help of entomologist Dr. Schmaedick of ASCC Land Grant.

III. Measurement of Fig Wasps' External Features

Out of the many fig wasps found, 5 males and 5 females were randomly selected out of the 75% ethanol to be measured. A Vision Engineering Cobra Expanded Pupil microscope with graticule was utilized in measuring the external features of the 10 fig wasps. The measurements were done at 80X magnification using the Vision Engineering Cobra Expanded Pupil microscope with 2X multiplier and 1X objective. Female fig wasps were measured according to their body length, head width, head length, 2 pairs of wings, antenna, and ovipositor. Male fig wasps' measurements include its body length, head width, head length, gaster, and mandible.

IV. Measurement of Fig Fruits

Newly collected fig fruits were being measured, because it would provide accurate measurements. The fig fruits were measured according to the length of the syconium and the thickness of the fig wall.

RESULTS

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