Integrative taxonomy improves understanding of native beneficial fauna: revision of the Nearctic Peristenus pallipes complex (Hymenoptera: Braconidae) and implications for release of exotic biocontrol agents

The Nearctic Peristenus pallipes complex (Hymenoptera: Braconidae) consists of two species groups that are further divided into nine species, separated largely using ecological rather than morphological differences. The species are re‐examined with an integrative approach using morphometric multivariate ratios, molecular (COI and CytB), and ecological data to test the validity of the nine species. The data support only three valid species [P. dayi Goulet, P. mellipes (Cresson) and P. howardi Shaw] rather than nine. New synonymies include: P. braunae Goulet under P. dayi Goulet 2006 syn.n. ; P. carcamoi Goulet, P. otaniae Goulet and P. pseudopallipes (Loan) under P. mellipes (Cresson) syn.n. , and finally P. broadbenti Goulet 2006 and P. gillespiei Goulet 2006 under P. howardi Shaw 1999 syn.n . In light of these taxonomic revisions, the biology and distributions of the Nearctic P. pallipes complex are updated, resulting in three morphologically variable, widespread, multivoltine species rather than nine largely univoltine species with patchy distributions. The integrative taxonomic approach used here allowed for a more accurate delineation of native fauna and their potential to be competitively displaced by foreign biocontrol agents.     

Comparative analysis of the reproductive biology of two Peristenus species (Hymenoptera: Braconidae), biological control agents of Lygus plant bugs (Hemiptera: Miridae)

Peristenus digoneutis Loan and Peristenus stygicus Loan, parasitoids of the European tarnished plant bug Lygus rugulipennis Poppius, are established in the United States for biological control of native North American Lygus species, and are being considered for deliberate release in Canada. High lifetime fecundity of parasitoids is considered a desirable attribute of biological control agents and therefore, an understanding of parasitoid reproductive biology is required. In the present study, the potential lifetime fecundity of both agents was compared under laboratory conditions to estimate the potential impact of Peristenus species on Lygus. Synovigenic P. digoneutis and P. stygicus females oviposited most actively in the first two weeks of their lifetime, with a maximum average daily oviposition rate after five days. The maximum number of eggs laid per day was 83 eggs for P. stygicus, and 36 eggs for P. digoneutis. P. digoneutis has an average potential lifetime fecundity of 385 ± 35 SE eggs produced over 22 ± 3 SE days. In contrast, P. stygicus females have a 50% higher mean potential lifetime fecundity reaching 782 ± 65 SE eggs over 28 ± 1 SE days. A positive correlation between lifetime fecundity and body size was found only for P. stygicus, and both species showed a significant relationship between lifetime fecundity and oviposition period. The present study demonstrates that the fecundity of P. digoneutis and P. stygicus is considerably higher than previously reported. Based on these findings, P. stygicus appears to be the most effective biological control agent for Lygus lineolaris (Palisot de Beauvois) when only fecundity is taken into consideration.     

Changes in abundance of native and introduced parasites (Hymenoptera: Braconidae), and of the target and non-target plant bug species (Hemiptera: Miridae), during two classical biological control programs in alfalfa.

High numbers of tarnished plant bugs [Lygus lineolaris (Palisot)], were once common in alfalfa, as was a low level of parasitism (9%) by the native Peristenus pallipes (Curtis). After the bivoltine European parasite Peristenus digoneutis Loan became well established, average parasitism of the first and second generations increased to 64%, and tarnished plant bug numbers dropped by 65%. This reduced host density eventually caused a decline in total parasitism by both parasite species to 22%. A few P. digoneutis also attacked the alfalfa plant bug, Adelphocoris lineolatus (Goeze), but did not reduce this pest or increase its parasitism rate. At another location, where P. digoneutis is not established, parasitism of first generation alfalfa plant bugs, an adventive (accidently introduced) pest, was increased to 21% by the introduced univoltine parasite, Peristenus conradi Marsh, and a slight reduction in the pest may have resulted. P. digoneutis did not parasitize the meadow plant bug, Leptopterna dolabrata (L.), an adventive pest of forage grasses, so did not affect this mirid or its parasite. Neither introduced parasite eliminated the native parasites of the tarnished or alfalfa plant bugs. The narrow host ranges of the braconid parasites of mirid nymphs are contrasted with the broad host range of the native tachinid parasite [Phasia robertsoni (Towns.)] of adult mirids. The major changes in mirid abundance and their mortality by parasites that slowly occurred during this 19-year study demonstrate the need for long-term field research, to adequately document and understand these complex interactions.     

Length‐weight relationship of two Ambassid fish species,Parambassis dayi (Bleeker, 1874) and Parambassis thomassi (Day, 1870) from River Pamba,Southern Western Ghats,India

The present study provides the length‐weight relationships (LWRs) of two Ambassid fish species, Parambassis dayi (Bleeker, 1874) and Parambassis thomassi (Day, 1870) from River Pamba in Southern Western Ghats, India. Fishes were collected on a monthly basis between April 2014 to March 2015 using gill nets (1.0–3.0 cm), cast nets (1.0–2.0 cm) and seine nets (1.0 cm). The b values in the LWRs were estimated as 3.01 for P. dayi and 3.14 for P. thomassi. No previous information is available on LWRs for these two species in FishBase.     

The content of protein,fibre and minerals of leaves of selected Acacia species indigenous to north-western Tanzania

Abstract

Browse tree leaves of six species of Acacia (A. angustissima L., A. drepanolobium L., A. nilotica L., A. polyacantha L., A. senegal L., A. tortilis L.) were screened for chemical composition, including minerals and trace elements. Crude protein (CP) varied among the species from 145 (A. senegal) to 229 g/kg DM (A. angustissima). The species had moderate to high levels of minerals. The concentrations of Ca, P, Mg and S varied among the species from 14.6 – 31.5, 3.5 – 4.9, 1.4 – 3.0 and 1.7 – 2.8 g/kg DM, respectively. The forages showed relatively low concentrations of trace elements. Content of trace elements varied among the species from 4.5 – 23.8, 99.4 – 173.6, 146.2 – 432, 41.0 – 90.1, 10.9 – 22.2 and 0.05 – 0.65 mg/kg DM for Cu, Mo, Fe, Mn, Zn and Co, respectively. All leaves of browse species would meet the normal requirements for Ca, P, Mg and S in ruminants, although some species had higher levels of Ca than tabulated mineral requirements in livestock. Assayed Cu, Mn, Zn and Co would satisfy the lower range of recommended requirements of trace elements depending on their bioavailability. Therefore, browse leaves from Acacias could form good sources of CP and mineral supplements to ruminants.     

Detection of European Peristenus digoneutis loan in mirid populations in southern Ontario

Lygus spp. Hahn (Hemiptera: Miridae) are serious pests of a wide variety of economically important crops in North America. A European parasitoid, Peristenus digoneutis Loan (Hymenoptera: Braconidae), released in the northeastern USA for the biological control of Lygus, has successfully established in nine states and in eastern Canada, including southeastern Ontario, southern Quebec and Nova Scotia. To determine the extent to which P. digoneutis has dispersed and established in mirid populations in Ontario, a single-step multiplex PCR assay, designed to differentiate European species P. digoneutis and P. relictus from native North American Peristenus species, was used to identify parasitoid larvae dissected from field-collected Miridae. A total of 222 parasitoid larvae were analysed with the multiplex assay. Most (172) were identified as members of the P. pallipes Curtis complex; however, three from the Niagara region were identified as P. digoneutis. Specimens that did not amplify using the Peristenus multiplex PCR assay were screened with a PCR primer set designed to detect Leiophron (Hymenoptera: Braconidae) species, and most were confirmed to be Leiophron larvae. This study confirms the presence of P. digoneutis species in southern Ontario, and is another example of the utility of molecular methods for the detection of newly introduced or dispersed parasitoids. The presence of exotic P. digoneutis in southern Ontario may expedite future releases to augment already-established populations. Following such releases, the Peristenus multiplex PCR assay will be a useful component of post-release studies to evaluate the success of the biological control programme for Lygus plant bugs in Canada.     

Intrinsic competition between Diachasmimorpha longicaudata and three native species of parasitoids (Hymenoptera: Braconidae: Opiinae) of Anastrepha (Diptera: Tephritidae) fruit flies under laboratory conditions

The effect of intrinsic competition between the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) and the native species Doryctobracon crawfordi (Viereck), Utetes anastrephae (Viereck) and Opius hirtus (Fischer) (all Braconidae: Opiinae) was studied under laboratory conditions. Each native species and D. longicaudata acted as both a resident and an invader, and all species were introduced to the host simultaneously. Diachasmimorpha longicaudata was found to be the most competitive species because it achieved the highest parasitism percentage under all the experimental conditions, but it was also negatively affected by the presence and parasitic activity of the native parasitoids. Utetes anastrephae was the only species that maintained its parasitic rate when all species attacked the available hosts simultaneously. The emergence probability of a female D. longicaudata was positively associated with the increase in the number of scars on the cuticle of the host pupa, but this association was not observed for the native species. It was concluded that D. longicaudata is an intrinsic competitor that is superior to D. crawfordi, U. anastrephae and O. hirtus, whether acting as a resident or an invader, producing a female-biased sex ratio in all the evaluation conditions. Utetes anastrephae was the native species that was least affected by the competitive presence of D. longicaudata, which suggests that it could be used as a complementary biological control agent for Anastrepha fruit flies.     

Pre-release evaluation of absolute spillover impact risk of Physonota maculiventris (Chrysomelidae: Cassidinae) on non-target plant species Helianthus annuus (Asteraceae) and Zea mays (Poaceae) in South Africa

The tortoise beetle, Physonota maculiventris (Coleoptera: Chrysomelidae), a candidate biological control agent of Tithonia diversifolia (Hemsl.) A. Gray (Asteraceae) was screened for spillover risks on non-target plant species in South Africa. Studies were conducted to measure the absolute feeding damage and reproductive performance of P. maculiventris on non-target plant species, Helianthus annuus L. (Asteraceae) and Zea mays L. (Poaceae). The influence of spillover on generational build-up performance on the non-target plant species was also investigated. Adult female beetles were switched from T. diversifolia at 14 (actively feeding colony) or 24 (gravid colony) days to the non-target species. Likewise, as a backup or control, female beetles were exposed to H. annuus in a no-choice situation and switched to T. diversifolia and Z. mays. Feeding damage, adult longevity and egg production of P. maculiventris were significantly lower on H. annuus, compared to those metrics on T. diversifolia. Gravid P. maculiventris adults switched from T. diversifolia on the 14th day after emergence laid a few egg batches on the leaf surfaces of Z. mays, but no signs of feeding were observed. Furthermore, the population of P. maculiventris significantly increased by 11.7 fold (26.8–312.5 adults) between the first (F1) and second (F2) generations on T. diversifolia, while on the non-target, H. annuus, it decreased from 6.3 to zero (0). The study concludes that P. maculiventris will sustain its populations entirely on the target, T. diversifolia population stands associated with or without H. annuus and Z. mays cultivations at different scales in South Africa.     

Host range of Lepidelphax pistiae (Hemiptera: Delphacidae) and its potential impact on Pistia stratiotes L. (Araceae)

Pistia stratiotes L. (Araceae) is a floating aquatic plant that has become invasive in Florida. It is primarily controlled with herbicides, but two biocontrol agents have previously been released to assist in management of this species. A new potential biocontrol agent from Argentina, Lepidelphax pistiae Remes Lenicov (Hemiptera: Delphacidae), has been evaluated comprehensively for specificity after initial host range studies done in its native range indicated that it is likely specific to P. stratiotes. Host range studies indicated that this insect is specific to P. stratiotes, with no survival or reproduction occurring on any of the 42 other plant species tested. Impact studies indicated that this insect can significantly damage P. stratiotes at medium and high population densities, which were comparable to those seen in its native range. Lepidelphax pistiae is sufficiently specific enough to warrant release and has a high probability of aiding management of P. stratiotes populations in Florida.     

The impact of an invading alien grass (Agropyron cristatum) on species turnover in native prairie

Abstract. Alien invasions typically reduce species richness of habitats, but few studies have examined their effects on species turnover, the difference in species composition between localities. Agropyron cristatum (L.) Gaertn. (crested wheat grass) has been planted on 6–10 million ha of North American prairie, and is invading native prairie. We studied the invasion of A. cristatum into native prairie by measuring species composition along a gradient from maximum to minimum A. cristatum abundance. As A. cristatum increased, the abundance of most common native species decreased, but one appeared to be unaffected (Bouteloua gracilis (H.B.K.) Lag.), and another (Poa sandbergii Vasey) increased. The effect of A. cristatum on species turnover was investigated by examining species–area curves for areas from 0.5 m² to 8.0 m². Species diversity was reduced by 35% at high A. cristatum abundances at all areas. A. cristatum reduced the intercept of the species–area curve, but not the slope, suggesting that A. cristatum affected species turnover proportionally in all areas and habitats. This unusual result may indicate a homogeneous environment where species are distributed randomly. A. cristatum produced almost twice as many seeds as all native grasses combined. The number of seeds collected of native grasses and A. cristatum was highly correlated with the number of seed heads immediately nearby, but not with transect position. This suggests most seeds were dispersed over distances less than 5 m. In sum, the invasion of native prairie by A. cristatum might be related to high rates of seed production, and has the effect of decreasing species turnover by reducing the intercept of the species–area curve.     

First record of Ribes uva-crispa L. (Grossulariaceae) from the Madonie Mts., a new species of the Sicilian flora

Abstract

In this study, a first record of Ribes uva-crispa L. (Grossulariaceae) – a new species of the Sicilian flora – from the Madonie Mts. is reported. The autochthonous and relict new population of Ribes uva-crispa L. (Grossulariaceae) is found on Mount Carbonara (Madonie Mts., North-Central Sicily), which is several hundred kilometers away from the Central Apenninic and the South Mediterranean locations of its distribution range. R. uva-crispa shows a distribution similar to other taxa extending from the Euro-Asiatic area to the mountains of North Africa with disjunct populations on the main Sicilian reliefs (Madonie and Nebrodi Mts.), testifying ancient phytogeographical connections. This noteworthy record adds a new species – as well as a new genus and new family – to the vascular flora of Sicily. Based on the morphological characters, the population found is to be referred to Ribes uva-crispa L. subsp. austro-europaeum (Bornm.) Bech var. glanduligerum (Lindberg) Maire.     

Efficacy of chemical repellents against Otobius megnini (Acari: Argasidae) and three species of ixodid ticks

Otobius megnini (Dugès), often referred to as the ear tick or spinose ear tick, is a one-host tick native to the southwestern United States and Mexico. Infestations of this species can cause severe irritation and may affect breeding behavior in the host. Although chemical repellents are commonly used as an alternative approach to conventional arthropod vector control, information on repellency against O. megnini is lacking. This study compared repellency of ammonia, BioUD^®, 98.25 % DEET, garlic pepper tea, permanone, and pyrethrin with piperonyl butoxide, against larvae stages of O. megnini, Amblyomma americanum (L.), Dermacentor variabilis (Say), and Rhipicephalus sanguineus (Latreille). To test for repellency, tick movement was recorded at 30 s intervals for five min after introduction to a partially treated piece of filter paper. Results showed larvae of O. megnini exhibited less aversion to the chemicals tested when compared to the other tick species.     

Towards a characterization of the locomotor activity rhythm of the desertic species Porcellio olivieri (Crustacea,Isopoda) from Gabes (South of Tunisia)

The locomotor activity rhythm of the isopod, Porcellio olivieri, was investigated in Gannouch site in the south of Tunisia. The rhythm was monitored under constant temperature in individual animals in winter under two simultaneous regimens: the light–dark (LD) cycle and the continuous darkness (DD). Results revealed that whatever regimens, actograms, and mean activity curves showed that specimens of P. olivieri concentrated their activity during the experimental and subjective night. The species exhibited a locomotor rhythm period significantly shorter under LD (T = 23h13 ± 0h44) than DD (τ = 24h28 ± 0h58). However, the locomotor activity rhythm was less stable and the individuals were significantly more active under entraining conditions than constant darkness. The activity pattern of this species will be discussed as an adaptative strategy to respond to environmental conditions.     

Genetic architecture of the Tetragonula carbonaria species complex of Australian stingless bees (Hymenoptera: Apidae: Meliponini)

A species complex is a group of closely related species whose ecological or morphological boundaries are sufficiently vague that delimiting one species from another is difficult. In Australia, a group of four stingless bee species – Tetragonula carbonaria Smith, Tetragonula hockingsi Cockerell, Tetragonula mellipes Friese, and Tetragonula davenporti Franck – form a species complex in which gross morphology is clinal and overlapping. The species are most readily distinguished by the morphology of their brood combs. Here we genetically characterize bees sampled in areas where the species do and do not have contact. Our data corroborate previous evidence that T. hockingsi and T. carbonaria are genetically distinct and that there are two genetically distinct groups of T. hockingsi – one in the north and the other in the south of Queensland. Curiously, northern populations of T. hockingsi, which are allopatric to T. carbonaria, are genetically closer to T. carbonaria than are southern populations of T. hockingsi, which are in sympatry with T. carbonaria. We detected three hybrid colonies that appear to have arisen because of anthropogenic movement of T. hockingsi colonies from north to south of Queensland where males mated with local T. carbonaria queens. We discuss the status of T. davenporti, a recently described species cryptically similar to T. hockingsi from south‐east Queensland. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 149–161.     

PCR-based,rapid diagnosis of parasitism of Lygus spp. (Hemiptera: Miridae) by Peristenus relictus (Hymenoptera: Braconidae)

Several species of Lygus (Heteroptera: Miridae: Mirini) are serious crop pests in North America where their parasitism rate by native nymphal parasitoids is generally lower than in Europe. Peristenus relictus (Ruthe) (formerly P. stygicus Loan) (Hymenoptera: Braconidae: Euphorinae) is the predominant nymphal parasitoid of several Lygus spp. in the warm Mediterranean region and has been a candidate for introduction against Lygus hesperus Knight and L. lineolaris (Palisot de Beauvois) in the southern US. We report a rapid, sensitive, and specific PCR-based assay for diagnosis of P. relictus immature stages within Lygus nymphs that entails three steps: DNA extraction, PCR of the partial mitochondrial COI gene, and agarose gel electrophoresis. The PCR-based methodology is species-specific because the target DNA of other sympatric, congeneric species was not amplified with use of the primers developed for P. relictus diagnosis. The sensitivity of the PCR method, assessed through spike tests, was established by the detection of a ratio of 1:10,000 P. relictus DNA to Lygus DNA. Molecular diagnosis of parasitism of field collected nymphs is achievable in one day, eliminating the need to rear nymphs to obtain adult parasitoids for morphological identification.     

Ecophysiological and species‐specific responses to seasonal variations in halophytic species of the chenopodiaceae in a Mediterranean salt marsh

Plants adopt different strategies in response to seasonal variations in their natural biotype. In this study, the responses of seasonal changes on the organic osmolyte contents, ionic homoeostasis, osmotic potential and succulence of native chenopods in a salt marsh of Egypt were studied. Five halophytic species of the chenopodiaceae were collected during the rainy and dry season: Atriplex halimus L., Halocnemum strobilaceum (Pall.), Salicornia fruticosa (L.), Suaeda pruinosa (Lange) and Arthrocnemum macrostachyum (Moric). Results showed that plants employ an osmoconformer strategy via species specificity of response to seasonal variations. The total ions accumulation in all species was higher during the rainy season compared with the dry season. In particular, during rainy season, A. halimus resulted the higher accumulator species, followed by H. strobilaceum. Conversely, S. fruticosa, S. pruinosa and A. macrostachyum were defined as low‐accumulator species. In each studied species, the effective salinity, biological absorption coefficient as well as leaf succulence were higher during the rainy season. In conclusion, the present study have pointed out the importance that should be accorded with the development of research directed towards agronomic aspects for the uses of halophytic chenopodiaceae in salt marsh. Further, data obtained indicate that the ions accumulator species should be considered for use in phytoremediation of degraded saline lands.     

Variation in fine root biomass of three European tree species: Beech (Fagus sylvatica L.), Norway spruce (Picea abies L. Karst.), and Scots pine (Pinus sylvestris L.)

Abstract

Fine roots (<2 mm) are very dynamic and play a key role in forest ecosystem carbon and nutrient cycling and accumulation. We reviewed root biomass data of three main European tree species European beech, (Fagus sylvatica L.), Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.), in order to identify the differences between species, and within and between vegetation zones, and to show the relationships between root biomass and the climatic, site and stand factors. The collected literature consisted of data from 36 beech, 71 spruce and 43 pine stands. The mean fine root biomass of beech was 389 g m^?2, and that of spruce and pine 297 g m^?2 and 277 g m^?2, respectively. Data from pine stands supported the hypothesis that root biomass is higher in the temperate than in the boreal zone. The results indicated that the root biomass of deciduous trees is higher than that of conifers. The correlations between root biomass and site fertility characteristics seemed to be species specific. There was no correlation between soil acidity and root biomass. Beech fine root biomass decreased with stand age whereas pine root biomass increased with stand age. Fine root biomass at tree level correlated better than stand level root biomass with stand characteristics. The results showed that there exists a strong relationship between the fine root biomass and the above-ground biomass.     

Adult activity and oviposition of corn rootworms,Diabrotica spp. (Coleoptera: Chrysomelidae), in Miscanthus,corn and switchgrass

The ability of the biomass crop Miscanthus (Miscanthus × giganteus Greef and Deuter ex Hodkinson and Renvoize) to support larval development for both United States and European populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, suggests an avenue for interactions with corn (Zea mays L.). To provide context to survival of D. v. virgifera on Miscanthus, adult activity and oviposition of Diabrotica spp. were monitored in central Illinois in 2010–2011 in Miscanthus, corn and switchgrass (Panicum virgatum L.). For D. v. virgifera, vial traps within corn plots captured 3–10 times as many adults as in Miscanthus or switchgrass, while soil samples showed females laid approximately 10 times as many eggs in corn as in the perennial grasses. Adult southern corn rootworms, Diabrotica undecimpunctata howardi Barber, were the most abundant species in 2010 and clearly preferred switchgrass as an adult habitat, with vial traps in switchgrass capturing 5–10 times as many D. u. howardi as those in corn or Miscanthus. Based on the small production areas for Miscanthus and switchgrass (and low use of both by D. v. virgifera), it seems likely that there are no current impacts of these perennial grasses on pest status of Diabrotica spp. in corn or other crops. However, adaptations by Diabrotica spp. to pest management practices suggest they could be a source for interactions between biomass and food or feed crops. Early‐season soil samples did not recover eggs of D. u. howardi, but their use of switchgrass as an adult habitat suggests additional research in areas where switchgrass may be grown near peanuts, alfalfa or other hosts may be needed. Also, investigation of other candidate bioenergy crops known to support Diabrotica spp. larval development is needed to better understand the possible effects of a changing agricultural landscape on corn rootworms.