Nematodes Associated with Fig Wasps,Pegoscapus spp. (Agaonidae), and Syconia of Native Floridian Figs (Ficus spp.)

Syconia in successive developmental phases from Ficus laevigata Vahl (F. citrifolia Miller sensu DeWolf 1960) (Moraceae) and successive life stages of its fig wasp pollinator, Pegoscapus sp. (P. assuetus (Grandi) sensu Wiebes 1983) (Agaonidae) were dissected to elucidate their association with two undescribed species of nematodes. Parasitodiplogazter sp. (Diplogasteridae) are transported by female Pegoscapus sp. into the cavity of a phase B syconium as third-stage juveniles (J3), where they molt to the J4 stage and greatly increase in size in the hemocoel of the fig wasp after it begins to pollinate and oviposit in female florets. The J4 exit the wasp cadaver in a phase B or early phase C syconium, and molt to adults that mate and lay eggs. New J3 infect the next generation of female or male wasps as they emerge from their galls in phase D figs. Mated entomogenous females of Schistonchus sp. (Aphelenchoididae) are transported in the hemocoel of female wasps to the fig cavity of a phase B syconium. Female Schistonchus sp. exit the wasp and parasitize immature male florets causing an exudate, the development of hypertrophied epidermal cells of the anther filaments and anthers, and aberrations of the anther filament, anthers, and pollen. At least one generation of Schistonchus sp. occurs in the male florets. Entomogenous females appear at about the time that fig wasps molt to adults in their galls in late phase C syconia. Another Schistonchus sp. was recovered from females of P. mexicanus (Ashmead) (P. jimenezi (Grandi) sensu Wiebes 1983) and from the syconia of F. aurea Nuttall and appears to have a life cycle similar to that described for the Schistonchus sp. from F. laevigata.     

Differential Response to Root-Knot Nematodes in Prunus Species and Correlative Genetic Implications

Responses of 17 Prunus rootstocks or accessions (11 from the subgenus Amygdalus and 6 from the subgenus Prunophora) were evaluated against 11 isolates of Meloidogyne spp. including one M. arenaria, four M. incognita, four M. javanica, one M. hispanica, and an unclassified population from Florida. Characterization of plant response to root-knot nematodes was based on a gall index rating. Numbers of females and juveniles plus eggs in the roots were determined for 10 of the rootstocks evaluated against one M. arenaria, one M. incognita, one M. javanica, and the Florida isolate. These 10 rootstocks plus Nemaguard and Nemared were retested by growing three different rootstock genotypes together in containers of soil infested individually with each of the above four isolates. Garfi and Garrigues almonds, GF.305 and Rutgers Red Leaf peaches, and the peach-almond GF.677 were susceptible to all isolates. Differences in resistance were detected among the other rootstocks of the subgenus Amygdalus. The peach-almond GF.557 and Summergrand peach were resistant to M. arenaria and M. incognita but susceptible to M. javanica and the Florida isolate. Nemaguard, Nemared, and its two hybrids G x N no. 15 and G x N no. 22 were resistant to all but the Florida isolate. In the subgenus Prunophora, Myrobalan plums P.1079, P.2175, P.2980, and P.2984; Marianna plum 29C; and P. insititia plum AD.101 were resistant to all isolates. Thus, two different genetic systems of RKN resistance were found in the subgenus Amygdalus: one system acting against M. arenaria and M. incognita, and another system also acting against M. javanica. Prunophora rootstocks bear a complete genetic system for resistance also acting against the Florida isolate. The hypotheses on the relationships between these systems and the corresponding putative genes of resistance are presented.     

Schistonchus africanus n. sp. (Aphelenchida: Aphelenchoididae) Associated with Ficus thonningii (Moraceae) and its Pollinator Wasp Elisabethiella stuckenbergi (Chalcidoidea: Agaonidae)

Syconia ("figs") from Ficus thonningii and adults of its pollinator wasp Elisabethiella stuckenbergi were dissected to elucidate their association with a new species of Schistonchus (Aphelenchoididae). Schistonchus africanus n. sp. is characterized by a short stylet (13-16 μm long); position of the excretory pore opening in both sexes at a level just behind the stylet knobs; and short post-uterine branch, one body-width long. Schistonchus africanus n. sp. parasitizes F. thonningii florets and is transported by the winged females of E. stuckenbergi. Juveniles, females, and males of the nematode were found in the female and male fig florets and in the abdomen of the vector. Nematode populations extracted from female wasps or fig floret tissues did not differ in their morphology. No association was observed with the wingless males of the pollinator wasp.     

Leaf epidermal studies in some Nigerian species of Ficus L. (Moraceae)

Forty-two leaf epidermal features in 20 Nigerian species of Ficus, representing three of the four subgenera and four of the seven sections of the genus found in Africa have been examined. Discontinuities in these characters clearly separated the three subgenera studied, namely, Ficus, Sycomorus and Urostigma, and supported the earlier sectional classification of the subgenus Urostigma (i.e. sections Sycidium, Galoglychia and Urostigma). The subsectional boundaries among the members of the section Galoglychia studied, however, had little backing from their leaf epidermal characteristics due to extensive overlap of the features. The results of the present studies support the genetic basis of the qualitative and quantitative variations in the leaf epidermal cells, stomata and trichomes in the Nigerian Ficus and the present and potential applications of these features in diagnostic and taxonomic investigations in the genus are discussed.     

Biogeography and conservation of the genus Ficus (Moraceae) in Mexico

Aim The main objective of this study is to document the biogeographical patterns, endemism and degree of conservation of the species of Ficus (Moraceae) in Mexico. There are over 750 species of the genus Ficus distributed worldwide, and Mexico practically represents its northernmost limit in the American continent. Detailed studies at regional scales may help to understand the biogeography of large genera such as Ficus. Location Mexico. Methods The biogeographical patterns of Mexican Ficus were obtained from information of fig specimens available in two of the main herbaria of Mexico (2140 vouchers), collecting figs throughout this country, and revising the specialized literature. The presence of each species of Ficus was recorded for every one of Mexico's states and several tropical countries of America. Besides, the Mexican territory was divided into cells of 1° × 1° and the presence or absence of all species of the genus was recorded. Rarity of species was classified based on the width of geographic distribution, habitat specificity and population size. Results A total of 21 species of Ficus occur in Mexico, including six species (28.6%) that are endemic to this country. Five species are included in subgenus Pharmacosycea and 16 species are documented under subgenus Urostigma. Affinities of Ficus flora with other tropical countries in America generally decreased as geographical distances from Mexico increased. Mexican states and cells with highest values of Ficus species richness (both total and endemic species) were located. Ten species, including three endemics, presented a wide distribution. Five species, including two endemics, possess the three attributes of rarity (narrow geographical distribution, high habitat specificity and scarce local populations). Three species of Ficus, including the endemic and very rare Ficuslapathifolia (Liebm.) Miq., are not recorded in any protected area existing in Mexico. Main conclusions Most of the Mexican Ficus show a great morphological variation and occupy different habitats along their geographic distribution. The biogeographical patterns described here establish a fundamental scenario for ongoing studies on Ficus–pollinator interactions. However, many local populations are considered to be at risk, as there have been significant reductions in the number and size of local populations. Further studies are needed to understand the process of colonization, maintenance and persistence of fig–pollinator mutualism in species with different patterns of geographic distribution. Mexican Ficus require special policies for conservation due to their complex degree of rarity, particularly their geographic distribution in different types of vegetation, ranging from dry scrublands to tropical rain forests.     

Pericarp anatomy of wild roses (Rosa L., Rosaceae)

The pericarp anatomy of representatives of all subgenera and sections of the genus Rosa was studied. All species have the same basic pericarp structure: it is composed of inner and outer endocarps, mesocarp and exocarp formed by the epidermis and hypodermis. The differences concern mainly the thickness of particular layers, and the shape and size of their cells. Cells of the endocarp and mesocarp are thick-walled. The only exception is Rosa rugosa mesocarp, which is composed of rather thin-walled cells with a large lumen. The endocarp structure of Rosa achenes resembles the drupe of the genus Prunus s.l. and drupelets of Rubus species.     

Geographic and taxonomic distribution of a positive interaction: ant-tended homopterans indirectly benefit figs across southern Africa

Although species pairs and assemblages often occur across geographic regions, ecologists know very little about the outcome of their interactions on such large spatial scales. Here, we assess the geographic distribution and taxonomic diversity of a positive interaction involving ant-tended homopterans and fig trees in the genus Ficus. Previous experimental studies at a few locations in South Africa indicated that Ficus sur indirectly benefited from the presence of a homopteran (Hilda patruelis) because it attracted ants (primarily Pheidole megacephala) that reduced the effects of both pre-dispersal ovule gallers and parasitoids of pollinating wasps. Based on this work, we evaluated three conditions that must be met in order to support the hypothesis that this indirect interaction involves many fig species and occurs throughout much of southern Africa and Madagascar. Data on 429 trees distributed among five countries indicated that 20 of 38 Ficus species, and 46% of all trees sampled, had ants on their figs. Members of the Sycomorus subgenus were significantly more likely to attract ants than those in the Urostigma subgenus, and ant-colonization levels on these species were significantly greater than for Urostigma species. On average, each ant-occupied F.sur tree had 37% of its fig crop colonized by ants, whereas the value was 24% for other Ficus species. H. patruelis was the most common source for attracting ants, although figs were also attacked by a range of other ant-tended homopterans. P. megacephala was significantly more common on figs than other ant species, being present on 58% of sampled trees. Ant densities commonly exceeded 4.5 per fig, which a field experiment indicated was sufficient to provide protection from ovule gallers and parasitoids of pollinators. Forty-nine percent of all colonized F. sur trees sampled had ant densities equal to or greater than 4.5 per fig, whereas this value was 23% for other Ficus species. We conclude that there is considerable evidence to suggest that this indirect interaction occurs across four southern African countries and Madagascar, and involves many Ficus species. Received: 11 December 1997 / Accepted: 6 April 1998     

Stomatal Ultrastructure, Molecular Phylogeny, and Description of Parasitodiplogaster laevigata n. sp. (Nematoda: Diplogastridae), a Parasite of Fig Wasps

Parasitodiplogaster comprises a potentially large radiation of nematode species that appear to be parasitically bound to their Agaonid fig wasp hosts, which are mutualistically associated in the syconia (figs) of the diverse plant genus Ficus. Parasitodiplogaster laevigata n. sp. is described and illustrated as an associate of the fig wasp, Pegoscapus sp. from Ficus laevigata from southern Florida. It is the first species of Parasitodiplogaster reported from North America and is closest to P. trigonema from F. trigonata from Panama. Parasitodiplogaster laevigata n. sp. can be differentiated from all described species of Parasitodiplogaster based on stomatal morphology (presence of a large dorsal and a right subventral tooth) in the adults of both sexes, molecular comparisons of two expansion segments (D2,D3) of the large subunit (LSU) rRNAgene, and fig-fig wasp host affinities. The ultrastructure of P. laevigata n. sp. was elucidated using TEM and SEM for comparisons with other species of Parasitodiplogaster. The stoma of P. laevigata n. sp. possesses a nonsegmented cheilostomal ring that connects to the longitudinal body musculature per- and interradially, a claw-like dorsal tooth, a right subventral tooth, and telostegostomatal apodemes arising from the dorsal side of each subventral sector. The unification of the pro-, meso-, and metastegostom with the gymnostom in P. laevigata n. sp. and further simplification in other described species may be due to derived adaptations associated with the internal parasitism of fig wasps.     

Comparative Disc-Electrophoretic Protein Analyses of Selected Meloidogyne,Ditylenchus, Heterodera and Aphelenchus spp.

Disc-electrophoretic separation of soluble proteins from whole nematode homogenates yielded band profiles useful for distinguishing selected species of Meloidogyne and Ditylenchus, and the genera Heterodera, and Aphelenchus. Certain protein bands were common to all the species of Meloidogyne, whereas other bands were specific. Meloidogyne spp. and Heterodera glycines shared some protein similarities, but other genera differed distinctly. Protein profiles of Meloidogyne spp. were not significantly altered by the host on which the nematode was cultured.     

Non‐pollinating Fig Wasps Decrease Pollinator and Seed Production in Ficus andicola (Moraceae)

Fig trees ( Ficus spp.) and Agaonine fig‐wasps participate in an obligate mutualism. Fig wasps can only develop within fig inflorescences (syconia) and they are the only organisms capable of pollinating fig flowers. Other non‐pollinating wasps that lay eggs by inserting their ovipositors from the outside can also develop in syconia. These parasitic wasps may be parasitoids of either pollinating or other non‐pollinating wasps, or form galls in fig flowers or other tissues. Depending on this interaction, parasitic wasps may have various effects on the production of pollinating wasps and seeds. Wasps in the genus Idarnes, which parasitize New World figs (subgenus Urostigma), have an effect on wasp production but not on seed production. Heterandrium spp., which have short ovipositors and lay on external flowers, are infrequent and no effect on seed production has been documented. In the Colombian Andes, Idarnes spp. and Heterandrium spp. are the most frequent parasites of the Ficus andicola — Pegoscapus sp. mutualism, affecting 62 and 43 percent of syconia, respectively. Controlling for other factors that influence wasp and seed production, such as number of foundresses, syconium size and tree, we found that Idarnes reduced pollinator production by almost half but did not reduce seed production, whereas Heterandrium reduced seed production by 40 percent, and marginally affected pollinator production. Our results provide the first clear documentation of Heterandrium spp. impact on fig seed production. Whether the relative abundance of this genus is a generalized phenomenon in montane forest remains to be determined.     

Natural foliar variegation without costs? The case of Begonia

Background and Aims

Foliar variegation is recognized as arising from two major mechanisms: leaf structure and pigment-related variegation. Begonia has species with a variety of natural foliar variegation patterns, providing diverse examples of this phenomenon. The aims of this work are to elucidate the mechanisms underlying different foliar variegation patterns in Begonia and to determine their physiological consequences.

Methods

Six species and one cultivar of Begonia were investigated. Light and electron microscopy revealed the leaf structure and ultrastructure of chloroplasts in green and light areas of variegated leaves. Maximum quantum yields of photosystem II were measured by chlorophyll fluorescence. Comparison with a cultivar of Ficus revealed key features distinguishing variegation mechanisms.

Key Results

Intercellular space above the chlorenchyma is the mechanism of variegation in these Begonia. This intercellular space can be located (a) below the adaxial epidermis or (b) below the adaxial water storage tissue (the first report for any taxa), creating light areas on a leaf. In addition, chlorenchyma cell shape and chloroplast distribution within chlorenchyma cells differ between light and green areas. Chloroplasts from both areas showed dense stacking of grana and stroma thylakoid membranes. The maximum quantum yield did not differ significantly between these areas, suggesting minimal loss of function with variegation. However, the absence of chloroplasts in light areas of leaves in the Ficus cultivar led to an extremely low quantum yield.

Conclusions

Variegation in these Begonia is structural, where light areas are created by internal reflection between air spaces and cells in a leaf. Two forms of air space structural variegation occur, distinguished by the location of the air spaces. Both forms may have a common origin in development where dermal tissue becomes loosely connected to mesophyll. Photosynthetic functioning is retained in light areas, and these areas do not include primary veins, potentially limiting the costs of variegation.     

Histological Studies of Ditylenchus africanus Within Peanut Pods

Ditylenchus africanus entered the immature pegs and pods of peanut (Arachis hypogaea cv. Sellie) at the peg-connection and subsequently invaded the parenchymatous regions of the hull exocarp and endocarp, and eventually the seed testa. The nematode caused malformations of the cells of infected tissues, cell wall breakage, and cell collapse. The damage appeared to be due to enzymatic activity. In some testae the entire parenchyma region, which aids in protection of the seed, was destroyed. In immature pods, the nematodes moved across the fibrous region of the mesocarp into the hull endocarp. In mature pods, however, the fibrous mesocarp of the hull was lignified and apparently was a barrier to penetration of the inner pod tissues. In late-harvested pods, increased numbers of eggs and anhydrobiotes were found in the hull tissues, and eggs in the seed testa, suggesting the onset of winter survival mechanisms of the nematode.     

Screening Subterranean Clover (Trifolium spp.) Germplasm for Resistance to Meloidogyne species

This study was conducted to identify lines of subterranean clover (Trifolium spp.) with resistance to Meloidogyne arenaria (Neal, 1989) Chitwood, 1949, race 1; M. incognita (Kofoid and White, 1919) Chitwood, 1949, race 3; and M. javanica (Treub, 1885) Chitwood, 1949. A collection of 134 subterranean clover lines was evaluated and all had intermediate to high susceptibility. Root galling was negatively correlated with both seed and dry matter yields. Soil fumigation significantly reduced the nematode population in the field. Results indicate there is limited genetic resistance to root-knot nematodes among subterranean clover lines. Alternative sources of variation for this trait should be investigated.     

Susceptibility of Several Common Subtropical Weeds to Meloidogyne arenaria,M. incognita,and M. javanica

Experiments were conducted in the greenhouse to assess root galling and egg production of three root-knot nematode species, Meloidogyne arenaria, M. incognita, and M. javanica, on several weeds common to Florida agricultural land. Weeds evaluated were Amaranthus retroflexus (redroot pigweed), Cyperus esculentus (yellow nutsedge), Eleusine indica (goosegrass), Portulaca oleracea (common purslane), and Solanum americanum (American black nightshade). Additionally, although it is recommended as a cover crop in southern regions of the U.S., Aeschynomene americana (American jointvetch) was evaluated as a weed following the detection of root galling in a heavy volunteer infestation of an experimental field in southeastern Florida. Weeds were propagated from seed and inoculated with 1000 nematode eggs when plants reached the two true-leaf stage. Tomato (Solanum lycopersicum ‘Rutgers’) was included as a positive control. Aeschynomene americana and P. oleracea roots supported the highest number of juveniles (J₂) and had the highest number of eggs/g of root for all three species of Meloidogyne tested. However, though P. oleracea supported very high root levels of the three nematode species tested, its fleshy roots did not exhibit severe gall symptoms. Low levels of apparent galling, combined with high egg production, increase the potential for P. oleracea to support populations of these three species of root-knot nematodes to a degree that may not be appropriately recognized. This research quantifies the impact of P. oleracea as a host for M. arenaria, M. incognita, and M. javanica compared to several other important weeds commonly found in Florida agricultural production, and the potential for A. americana to serve as an important weed host of the three species of root-knot nematode tested in southern regions of Florida.     

Leaf anatomy of Ficus subsection Urostigma (Moraceae)

Species of Ficus subsection Urostigma show much overlapping variation in vegetative morphology, which often precludes correct identification of the species. The aim of this study was to describe the leaf anatomical characters and their variation and to check their suitability for identification. Included were 41 samples belonging to 25 species of subsection Urostigma, four samples belonging to two species of section Leucogyne and one specimen of Ficus glaberrima subsp. siamensis of subsection Conosycea. Transverse sections of lamina, midrib and petiole and cuticular macerations were used, and the observed anatomical characters are described for each species. On the basis of a limited number of studied samples, leaf anatomy shows little variation within each species and each species has a unique combination of character states, facilitating identification. Ficus arnottiana shows some leaf anatomical characters that are quite different from those of other members of subsection Urostigma, including a multiple epidermis and enlarged lithocysts on both sides of the leaf. Both characters are generally considered as typical for Ficus subsection Conosycea. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 259–281.     

Greenhouse Studies on the Effect of Marigolds (Tagetes spp.) on Four Meloidogyne Species

The effects of preplanted marigold on tomato root galling and multiplication of Meloidogyne incognita, M. javanica, M. arenaria, and M. hapla were studied. Marigold cultivars of Tagetes patula, T. erecta, T. signata, and a Tagetes hybrid all reduced galling and numbers of second-stage juveniles in subsequent tomato compared to the tomato-tomato control. All four Meloidogyne spp. reproduced on T. signata ''Tangerine Gem''. Several cultivars of T. patula and T. erecta suppressed galling and reproduction of Meloidogyne spp. on tomato to levels lower than or comparable to a fallow control. Phytotoxic effects of marigold on tomato were not observed. Several of the tested marigold cultivars are ready for full-scale field evaluation against Meloidogyne spp.     

Susceptibility of Neoaplectana spp. and Heterorhabditis heliothidis to the Endoparasitic Fungus Drechmeria coniospora

Adhesive conidia of the nematophagous fungus, Drechmeria coniospora (Drechsler) W. Gams and Jansson (Moniliales: Deuteromycetes), would occasionally attach but never penetrate the infective stages of insect parasitic Neoaplectana carpocapsae, N. glaseri, N. bibionis, N. intermedia, and Heterorhabditis helfothidis (Rhabditida). However, adult and pre-infective stages of Neoaplectana spp. became infected by the fungus.