R. C. Wilkinson

Plasticity in life-history traits of the bark beetle Ips calligraphus as influenced by phloem thickness

SummaryReproduction and development of Ips calligraphus (Germar) (Coleoptera: Scolytidae) occur primarily in the phloem (inner bark) tissue of its pine hosts. In slash pine (Pinus elliottii Engelm. var. elliottii), phloem thickness can vary widely from tree to tree. We compared adult residence time and fecundity and progeny development time, body size, and sex ratio of this beetle when reared in slash pine bolts and bark slabs with phloem thicker or thinner than average adult body width. Most studies were conducted at 20°, 25°, and 30° C. Residence time of parent males and females decreased with increasing temperature but it was not affected by phloem thickness. Residence time of parent males was about 2 days shorter than that of parent females at each temperature. Reproductive fitness was greater in thick phloem at all temperatures as measured by faster larval development, earlier emergence of progeny (F1) adults, and emergence of more progeny adults per parent female. Progeny survival was similar between phloem those from thick phloem, and their sex ratio was female biased (1:2 vs 1:1, male:female). When allowed to inhabit thick phloem, the progeny (F2) of adults from thin phloem were just as large and of similar sex ratio (1:1) as were progeny of F1 adults from thick phloem. The high degree of plasticity in the life-history traits of this beetle may enable it to successfully colonize pines that vary widely in phloem thickness.

Secondary attraction and field activity of beetle-produced volatiles inDendroctonus terebrans

Controlled infestation ofDendroctonus terebrans (Olivier) on bolts of slash pine,Pinus ellionii Engelm. var.elliottii, elicited greater attraction of wild conspecifics than uninfested bolts. Secondary attraction was not apparent, however, to standing slash pines that had received volunteer attacks, when compared with attraction to unattacked but susceptible trees. Hindguts from in-flight or attacking femaleD. terebrans contained frontalin, and those from in-flight or attacking males containedexo-brevicomin.Trans-pinocarveol,cis-verbenol,trans-verbenol, myrtenal, verbenone, myrtenol, and other compounds were produced by both sexes during gallery construction in host trees. Synthetic frontalin, when deployed with a standard host odor mixture of turpentine and ethanol, was very attractive to maleD. terebrans in field-trapping experiments. The addition of eitherexo-brevicomin orendo-brevicomin to the frontalin-turpentine combination negated the attractive effect of frontalin for males.Trans-verbenol, myrtenol, and verbenone had little effect onD. terebrans behavior. Responses of females did not differ among treatments in any of the 11 field experiments.

Field and electroantennogram responses of the red-headed pine sawfly,Neodiprion lecontei (Fitch), to optical isomers of sawfly sex pheromones

Sawfly sex pheromones, the acetate and propionate esters of 3,7-dimethylpentadecan-2-ol, were field tested for activity towardNeodiprion lecontei (Fitch). Only the acetate form of the 2S,3S,7S isomer was active. Field catch decreased with the addition of the 2S,3R,7(R/S) acetate isomer sample. Electroantennogram recordings showed a positive correlation between response and degree to which the chirality of each isomer resembled the attractive isomer.

Field responses of redheaded pine sawfly males to a synthetic pheromone and virgin females in Florida.

Field tests using the sawfly pheromone [3,7-dimethylpentadecan-2-ol acetate with (−)-erythro configuration (2S,3S)] were conducted near Gainesville, Florida, during 1978–1981 to determine the attraction ofNeodiprion lecontei males to baited traps with respect to time of year and time of day. Greatest numbers of males were caught during May, July, and September in traps placed within a pine stand from July 1978 to July 1979. Males were only caught between 1400 and 2000 hr on 10 dates in June and 10 dates in September–October 1980, and 10 dates in June 1981, with greatest catches from 1600–1800 hr. Catches in a synthetic-baited trap and in virgin female-baited traps were similar with respect to time of day.

A Comparison of Sperm Health in Declining and Stable Populations of Hellbenders (Cryptobranchus alleganiensis alleganiensis and C.a. bishopi)

Abstract Animals in many freshwater habitats are experiencing decreased recruitment due to declines in reproductive health. Both subspecies of a long-lived aquatic salamander, (Cryptobranchus alleganiensis alleganiensis and C. a. bishopi) have experienced severe population declines characterized by low recruitment. For many states throughout their geographic range, captive propagation and translocation are the only remaining form of management given the severity of declines. These captive rearing programs should rely on techniques to assess male reproductive health, which are currently lacking. In this study, we compared the sperm health (motility, viability, and concentration) of male hellbenders from declining and stable populations. Sperm motility and viability were similar among populations, but sperm concentrations (sp/ml) were significantly lower in declining Missouri populations than in hellbenders from populations with higher recruitment in the southeast. Sperm from Ozark hellbenders was successfully cryopreserved but with low post thaw motilities. This method for assessing male reproductive health provides the first baseline comparative study among populations of this cryptic species in decline and has broad implications for use in monitoring male health across the distribution of the eastern hellbender.