Marc De Meyer

Geographic Distribution, Host Fruit, and Parasitoids of African Fruit Fly Pests Ceratitis anonae, Ceratitis cosyra, Ceratitis fasciventris, and Ceratitis rosa (Diptera: Tephritidae) in Kenya

Abstract The fruit of indigenous, cultivated, and naturalized exotic plants was sampled in Kenya to determine the geographical and host plant distributions of the fruit fly pests Ceratitis anonae (Graham), Ceratitis cosyra (Walker), Ceratitis fasciventris (Bezzi), and Ceratitis rosa Karsch. In 1997, cultivated and wild fruit were sampled on the Kenya coast to determine seasonal patterns of host use by C. cosyra and C. rosa. From 1999 to 2004, the sampling effort was expanded to forested areas of the central and western highlands and to all fruit-infesting tephritids. Together, the four pest tephritid species were reared from 5.1% of 3,794 fruit collections, the latter making up 116 families and 882 species of host plants. C. anonae, C. cosyra, C. fasciventris, and C. rosa were reared throughout Kenya, from 14, 9, 30, and 28 plant species, respectively. Fifty-two of these plants represented previously unknown hosts for one or more of the tephritids. C. anonae was restricted to habitats west of the Gregory Rift Valley. C. fasciventris was found in western and central Kenya, but it was not reared from coastal fruit collections. C. rosa occurred at the coast and in central highland fruit. We provide evidence for the recent introduction of C. rosa into the central highlands. Only C. cosyra was found in habitats located in all three of the major regions sampled. Although distributed over a wider geographic area than the other species, C. cosyra had a markedly restricted host range. On the coast, C. cosyra used wild fruit, primarily Sclerocarya birrea (A. Rich.) Hochst. (Anacardiaceae), as hosts when mango was not fruiting. C. rosa was absent from our mango samples but attacked common guava and wild fruit species. Overall, C. anonae, C. fasciventris, and C. rosa had similar host profiles, but each also had unique hosts in which infestations were usually heavy. Members of the Sapotaceae and Annonaceae were the most important wild hosts of these three species. Within these families, host fruit were partitioned among these tephritid species and the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). The availability of wild host fruit, sometimes supplemented by naturalized invasive plants or cultivated fruit, provided for year-round breeding of C. anonae and C. fasciventris, whereas indigenous fruit were sufficient for breeding of C. rosa and C. cosyra during most of the year. Opiine braconids were reared from all four species of Ceratitis.

Indigenous hosts of Ceratitis capitata (Diptera: Tephritidae) in Kenya.

Abstract To study the relationship of Mediterranean fruit fly or medfly, Ceratitis capitata (Wiedemann), to native plant hosts in an area within its original home range, fruits were sampled in diverse areas of Kenya from 1999 to 2001. Sampling effort was concentrated in and around forested areas in coastal, central highland, and western highland habitats. Medflies were reared from fruits of 55 species of plants, 51 of them indigenous; 46 of these species represent previously unknown hosts in Africa. Fruits infested by C. capitata were collected in all study sites, east and west of the Gregory Rift Valley, in xeric habitats between the coast and the central highlands, and at altitudes from sea level to 2,164 m above sea level. The conditions for year-round breeding of medfly in indigenous fruits are present at the coast, and possibly in highland areas as well. Infestation indices were comparable to those reported elsewhere from cultivated fruits. Although polyphagous in its home range, C. capitata was not distributed uniformly among species within two important host-plant families, Sapotaceae and Rubiaceae.

Strongly diverging population genetic patterns of three skipper species: the role of habitat fragmentation and dispersal ability

The fragmentation of landscapes has an important impact on the conservation of biodiversity, and the genetic diversity is an important factor for a populations viability, influenced by the landscape structure. However, different species with differing ecological demands react rather different on the same landscape pattern. To address this feature, we studied three skipper species with differing habitat requirements (Lulworth Skipper Thymelicus acteon: a habitat specialist with low dispersal ability, Small Skipper Thymelicus sylvestris: a habitat generalist with low dispersal ability, Essex Skipper Thymelicus lineola: a habitat generalist with higher dispersal ability). We analysed 18 allozyme loci for 1,063 individuals in our western German study region with adjoining areas in Luxembourg and north-eastern France. The genetic diversity of all three species were intermediate in comparison with other butterfly species. The FST was relatively high for T. acteon (5.1%), low for T. sylvestris (1.6%) and not significant for T. lineola. Isolation by distance analyses revealed a significant correlation for T. sylvestris explaining 20.3% of its differentiation, but no such structure was found for the two other species. Most likely, the high dispersal ability of T. lineola in comparison with T. sylvestris leads to a more or less panmictic structure and hence impedes isolation by distance. On the other hand, the isolation of the populations of T. acteon seems to be so strict that the populations develop independently. Although no general genetic impoverishing was observed for the endangered T. acteon, small populations had significantly lower genetic diversities than big populations, and therefore the high degree of isolation among populations might threaten its local and regional survival.

Higher phylogeny of frugivorous flies (Diptera, Tephritidae, Dacini): Localised partition conflicts and a novel generic classification

The phylogenetic relationships within and among subtribes of the fruit fly tribe Dacini (Ceratitidina, Dacina, Gastrozonina) were investigated by sequencing four mitochondrial and one nuclear gene fragment. Bayesian, maximum likelihood and maximum parsimony analyses were implemented on two datasets. The first, aiming at obtaining the strongest phylogenetic signal (yet, having lower taxon coverage), consisted of 98 vouchers and 2338 concatenated base pairs (bp). The second, aiming at obtaining the largest taxonomic coverage (yet, providing lower resolution), included 159 vouchers and 1200 concatenated bp. Phylogenetic relationships inferred by different tree reconstruction methods were largely congruent and showed a general agreement between concatenated tree topologies. Yet, local conflicts in phylogenetic signals evidenced a number of critical sectors in the phylogeny of Dacini fruit flies. All three Dacini subtribes were recovered as monophyletic. Yet, within the subtribe Ceratitidina only Perilampsis and Capparimyia formed well-resolved monophyletic groups while Ceratitis and Trirhithrum did not. Carpophthoromyia was paraphyletic because it included Trirhithrum demeyeri and Ceratitis connexa. Complex phylogenetic relationships and localised conflict in phylogenetic signals were observed within subtribe Dacina with (a) Dacus, (b) Bactrocera (Zeugodacus) and (c) all other Bactrocera species forming separate clades. The subgenus Bactrocera (Zeugodacus) is therefore raised to generic rank (Zeugodacus Hendel stat. nov.). Additionally, Bactrocera subgenera grouped under the Zeugodacus group should be considered under new generic combinations. Although there are indications that Zeugodacus and Dacus are sister groups, the exact relationship between Zeugodacus stat. nov., Dacus and Bactrocera still needs to be properly resolved.

Identifying Insects with Incomplete DNA Barcode Libraries, African Fruit Flies (Diptera: Tephritidae) as a Test Case

We propose a general working strategy to deal with incomplete reference libraries in the DNA barcoding identification of species. Considering that (1) queries with a large genetic distance with their best DNA barcode match are more likely to be misidentified and (2) imposing a distance threshold profitably reduces identification errors, we modelled relationships between identification performances and distance thresholds in four DNA barcode libraries of Diptera (n = 4270), Lepidoptera (n = 7577), Hymenoptera (n = 2067) and Tephritidae (n = 602 DNA barcodes). In all cases, more restrictive distance thresholds produced a gradual increase in the proportion of true negatives, a gradual decrease of false positives and more abrupt variations in the proportions of true positives and false negatives. More restrictive distance thresholds improved precision, yet negatively affected accuracy due to the higher proportions of queries discarded (viz. having a distance query-best match above the threshold). Using a simple linear regression we calculated an ad hoc distance threshold for the tephritid library producing an estimated relative identification error <0.05. According to the expectations, when we used this threshold for the identification of 188 independently collected tephritids, less than 5% of queries with a distance query-best match below the threshold were misidentified. Ad hoc thresholds can be calculated for each particular reference library of DNA barcodes and should be used as cut-off mark defining whether we can proceed identifying the query with a known estimated error probability (e.g. 5%) or whether we should discard the query and consider alternative/complementary identification methods.

Taxonomic Identity of the Invasive Fruit Fly Pest, Bactrocera invadens: Concordance in Morphometry and DNA Barcoding

In 2003, a new fruit fly pest species was recorded for the first time in Kenya and has subsequently been found in 28 countries across tropical Africa. The insect was described as Bactrocera invadens, due to its rapid invasion of the African continent. In this study, the morphometry and DNA Barcoding of different populations of B. invadens distributed across the species range of tropical Africa and a sample from the pests putative aboriginal home of Sri Lanka was investigated. Morphometry using wing veins and tibia length was used to separate B. invadens populations from other closely related Bactrocera species. The Principal component analysis yielded 15 components which correspond to the 15 morphometric measurements. The first two principal axes contributed to 90.7% of the total variance and showed partial separation of these populations. Canonical discriminant analysis indicated that only the first five canonical variates were statistically significant. The first two canonical variates contributed a total of 80.9% of the total variance clustering B. invadens with other members of the B. dorsalis complex while distinctly separating B. correcta, B. cucurbitae, B. oleae and B. zonata. The largest Mahalanobis squared distance (D2 = 122.9) was found to be between B. cucurbitae and B. zonata, while the lowest was observed between B. invadens populations against B. kandiensis (8.1) and against B. dorsalis s.s (11.4). Evolutionary history inferred by the Neighbor-Joining method clustered the Bactrocera species populations into four clusters. First cluster consisted of the B. dorsalis complex (B. invadens, B. kandiensis and B. dorsalis s. s.), branching from the same node while the second group was paraphyletic clades of B. correcta and B. zonata. The last two are monophyletic clades, consisting of B. cucurbitae and B. oleae, respectively. Principal component analysis using the genetic distances confirmed the clustering inferred by the NJ tree.

Choice of metrics for studying arthropod responses to habitat disturbance: one example from Gabon

Abstract.  1 The choice of metrics comparing pristine and disturbed habitats may not be straightforward. We examined the results of a study in Gabon including 21 arthropod focal taxa representing 16 855 individuals separated into 1534 morphospecies. Replication included the understorey of 12 sites representing four stages of land use after logging (old and young forests, savanna and gardens), surveyed for 1 year using three sampling methods. 2 For all focal taxa, we calculated a suite of 13 metrics accounting for the intensity of faunal changes between habitats, namely: abundance; observed, rarefied and estimated species richness; proportion of rare species; additive diversity partitioning; evenness of assemblages; higher taxonomic composition; species turnover; ordination scores of multivariate analyses; nestedness; proportion of site‐specific species and ratios of functional guilds. 3 Most metrics showed large differences between forests and non‐forest habitats, but were not equally discriminating for particular taxa. Despite higher taxonomic groups being present in most habitats, many insect species were site or habitat specific. There was little evidence that the disturbance gradient represented a series of impoverished habitats derived from older forests. Rather, entire suites of species were being replaced as habitats were modified. 4 Metrics based on species identity had a high sensitivity to disturbance, whereas measurements describing community structure were less discriminating in this regard. We recommend using metrics based on abundance, estimated species richness, species turnover estimated by multivariate analyses and guild structure, to avoid misleading interpretations that may result from comparisons of species richness alone.

Unprecedented long-term genetic monomorphism in an endangered relict butterfly species

Multi-locus monomorphism in microsatellites is practically non-existent, with one notable exception, the island fox (Urocyon littoralis dickeyi) population on San Nicolas island off the coast of southern California, having been called “the most monomorphic sexually reproducing animal population yet reported”. Here, we present the unprecedented long-term monomorphism in relict populations of the highly endangered Parnassius apollo butterfly, which is protected by CITES and classified as “threatened” by the IUCN. The species is disjunctly distributed throughout the western Palaearctic and has occurred in several small remnant populations outside its main distribution area. We screened 78 individuals from 1 such relict area (Mosel valley, Germany) at 16 allozyme and 6 microsatellite loci with the latter known to be polymorphic in this species elsewhere. From the same area, we also genotyped 55 museum specimens sampled from 1895 to 1989 to compare historical and present levels of genetic diversity. However, none of all these temporal populations yielded any polymorphism. Thus, present and historical butterflies were completely monomorphic for the same fixed allele. This is the second study to report multi-locus monomorphism for microsatellites in an animal population and the first one to prove this monomorphism not to be the consequence of recent factors. Possible explanations for our results are a very low long-term effective population size and/or a strong historic bottleneck or founder event. Since the studied population has just recovered from a recent population breakdown (second half of twentieth century) and no signs of inbreeding depression have been detected, natural selection might have purged the population of weakly deleterious alleles, thus rendering it less susceptible to the usual negative corollaries of high levels of homozygosity and low effective population size.

Revision of the subgenus Ceratitis (Pardalaspis) Bezzi, 1918 (Diptera, Tephritidae, Ceratitini)

Abstract. The fruit fly genus Ceratitis (Diptera: Tephritidae) comprises several important pest species attacking a wide range of unrelated fruits. In this paper the subgenus Ceratitis (Pardalaspis) Bezzi is revised. Ten species are recognized of which five are described as new: C.(P.)hamata sp.n., C.(P.)munroi sp.n., C.(P.)serrata sp.n., C.(P.)semipunctata sp.n. and C.(P.)zairensis sp.n. A key to both sexes is provided. All species are restricted to the Afrotropical Region and distributional and known host plant data are given.

A review of the current knowledge on Zeugodacus cucurbitae (Coquillett) (Diptera, Tephritidae) in Africa, with a list of species included in Zeugodacus

Abstract This paper reviews all available information regarding the occurrence and biology of the melon fly, Zeugodacus cucurbitae (Coquillett), in the Afrotropical Region, including data on invasion history, distribution patterns, population genetics, host range, and interspecific competition. Although limited intraspecific variability has been observed within the region regarding the above mentioned aspects, there seems to be no indication that Zeugodacus cucurbitae represents a species complex. A checklist of all of the species included in Zeugodacus as recently proposed by Virgilio et al. (2015) is provided.