by Dr. Molly Darr | Jun 7, 2022 | 2011-2020 Publications
Abstract
When related species coexist, selection pressure should favor evolution of species recognition mechanisms to prevent interspecific pairing and wasteful reproductive encounters. We investigated the potential role of pheromone and acoustic signals in species recognition between two species of tree-killing bark beetles, the southern pine beetle, Dendroctonus frontalis Zimmermann, and the western pine beetle, Dendroctonus brevicomis LeConte, in a narrow zone of sympatry, using reciprocal pairing experiments. Given the choice of adjacent con- or heterospecific female gallery entrance in a log, at least 85% of walking males chose the entrance of the conspecific, and half the males that initially entered heterospecific galleries re-emerged and entered the conspecific gallery within 15 min. Waveform analysis of female acoustic “chirps” indicated interspecific differences in chirp timing. Males may use information from female acoustic signals to decide whether to enter or remain in the gallery. Individuals in forced heterospecific pairings (produced by confinement of a heterospecific male within the female entrance) did not differ in pheromone production from individuals of conspecific pairs. However, due to the absence of the right species of male, galleries with heterospecific pairs released an abnormal pheromone blend that lacked at least one key component of the aggregation pheromone of either species. The complete aggregation pheromone (i.e., the pheromone blend from entrances with pairs) does not appear to deter interspecific encounters or confer premating reproductive isolation per se; however, it may confer selective pressure for the maintenance of other reproductive isolation mechanisms.
Keywords
acoustic signal, character displacement, Dendroctonus, multispecies aggregation, pheromone
To read the full article please visit the link below:
Pureswaran, Deepa S., Richard W. Hofstetter, Brian T. Sullivan, and Kristen A. Potter. 2016. “The Role of Multimodal Signals in Species Recognition Between Tree-Killing Bark Beetles in a Narrow Sympatric Zone.” Environmental Entomology 45 (3): 582–91. https://doi.org/10.1093/ee/nvw022.
by Dr. Molly Darr | Jun 7, 2022 | 2011-2020 Publications
Abstract
We collected, identified, and quantified volatiles arising from individual gallery entrances of the monogamous bark beetle Dendroctonus frontalis Zimmermann. Samples were collected while the insects were mass attacking mature loblolly pines (Pinus taeda L.) in an established infestation in western Mississippi, 1 August through 3 October 2005. Following volatile sample
collection, the entrances were dissected and categorized according to those that 1) contained a solitary female (the gallery initiating sex), 2) contained a pair that had not yet produced an egg gallery, 3) led to an egg gallery with niches and/or eggs, or 4) represented failed attacks (either abandoned or containing dead beetles). The greatest mean release rate of the female-produced aggregation pheromone components frontalin (74 ng/h) and trans-verbenol (0.35 μg/h) was detected from entrances of solitary females, whereas the highest mean quantities of the male-produced multifunctional pheromone components endo-brevicomin (18 ng/h) and verbenone (0.15 μg/h) were detected from entrances of preoviposition beetle pairs. Alpha-pinene, a host-produced monoterpene that functions
as a synergist for the aggregation attractant for D. frontalis, was detected from entrances of solitary females and preoviposition pairs at a rate of 0.6 mg/h, or 3Ð4 orders of magnitude greater than the insect-produced components of the attractant. Our results indicate that the release rates of pheromone components used in published field studies of the chemical ecology of D. frontalis (generally >0.1 mg/h) represent thousands of ‘attack equivalents’ or production rates on the scale of a beetle mass attack on a single host. Additionally, our data suggest that the loss in attractiveness of host tissue fully colonized by D. frontalis is because of the disappearance of attractants rather than an increase in inhibitors.
Keywords
semiochemical release rate, mass attack, attack phase, synthetic lure, mass trapping
To read the full article please visit the link below:
Pureswaran, Deepa S., Richard W. Hofstetter, Brian T. Sullivan, and Kristen A. Potter. 2016. “The Role of Multimodal Signals in Species Recognition Between Tree-Killing Bark Beetles in a Narrow Sympatric Zone.” Environmental Entomology 45 (3): 582–91. https://doi.org/10.1093/ee/nvw022.
by Dr. Molly Darr | Jun 7, 2022 | 2011-2020 Publications
Abstract
Previous studies of nonindustrial private forest (NIPF) landowners examined factors affecting their management decisions such as harvesting, selling land, and enrolling in cost-share programs. Converting forestland into nonforest uses, however, is yet another important and perhaps more critical decision that could have irreversible impacts on forest resources. Understanding factors that directly or indirectly influence such decisions would be important in curbing the conversion rate, which is believed to be increasing rapidly in some of the privately owned forest landscapes in the US South. This study used a discrete choice model of forestland conversion decision on data collected from a survey of NIPF landowners in the Cumberland Plateau of Tennessee to investigate the factors related with a landowner’s decision to convert forestland. Results reveal that landowners’ decisions to convert forestland were significantly influenced by sociodemographic factors, ownership characteristics, and expected land returns from forestry and alternative land uses. Further, timber damage due to a native pest (southern pine beetle) increased the probability of conversion,
whereas the motivation of landowners to pass the property to heirs decreased it. These findings will be useful for forestry professionals and extension specialists trying to understand the characteristics as well as motivations of landowners who are changing their forest land-use decisions.
Keywords
land rent, probit model, land-use change
To read the full article please visit the link below:
Poudyal, Neelam C., Omkar Joshi, Donald G. Hodges, and Kevin Hoyt. 2014. “Factors Related with Nonindustrial Private Forest Landowners’ Forest Conversion Decision in Cumberland Plateau, Tennessee.” Forest Science 60 (5): 988–93. https://doi.org/10.5849/forsci.13-622.
by Dr. Molly Darr | Jun 7, 2022 | 2011-2020 Publications
Abstract
Since 2003, the Southern Pine Beetle Prevention Program (SPBPP) (a joint effort of the USDA Forest Service and
Southern Group of State Foresters) has encouraged and provided cost-share assistance for silvicultural treatments to
reduce stand/forest susceptibility to the southern pine beetle (SPB) (Dendroctonus frontalis Zimmermann) in the
southeastern United States. Until now, stand- and landscape-level tests of this program’s efficacy were nonexistent. In
2012, SPB outbreaks occurred in the Homochitto and Bienville National Forests (NFs) in Mississippi. Parts of each NF
were treated (thinned) using SPBPP management recommendations, whereas other areas were untreated (unthinned).
In the Homochitto NF, 99.7% of SPB spots occurred in unthinned stands, whereas all SPB spots occurred in unthinned
stands in the Bienville NF. Unthinned stands in both NFs had higher basal area, higher stocking, and lower growth rates
over the last decade. Burning also resulted in a lower incidence of SPB infestation. Our retrospective study results
validate the effectiveness of SPBPP treatments for reducing stand- and landscape-level susceptibility to SPB, which
encourages proper silvicultural methods that increase tree spacing, growth, and vitality, while effectively altering the
in-stand atmosphere enough to interfere with SPB pheromone communication, thus reducing susceptibility to SPB spot
initiation and spread.
Keywords
bark beetles, Dendroctonus frontalis, forest management, Pinus taeda, silviculture, Southern Pine
Beetle Prevention Program
To read the full article please visit the link below:
Nowak, John T., James R. Meeker, David R. Coyle, Chris A. Steiner, and Cavell Brownie. 2015. “Southern Pine Beetle Infestations in Relation to Forest Stand Conditions, Previous Thinning, and Prescribed Burning: Evaluation of the Southern Pine Beetle Prevention Program.” Journal of Forestry 113 (5): 454–62. https://doi.org/10.5849/jof.15-002.
by Dr. Molly Darr | Jun 7, 2022 | 2011-2020 Publications
Abstract
In the Central American region, the aggressive, sibling bark beetles Dendroctonus frontalis Zimmermann (Coleoptera:
Curculionidae: Scolytinae) and Dendroctonus mesoamericanus Armendáriz-Toledano & Sullivan (Coleoptera:
Curculionidae: Scolytinae) commonly colonize pines concurrently, and in nature they avoid heterospecific pairing,
although it can be produced in the lab. We performed walking arrestment bioassays in the lab to examine the
capacity of both sexes of both species to discriminate odors from frass expelled from gallery entrances of either
solitary females or conspecific pairs of either species. Males of both species strongly preferred odors of frass from
solitary, conspecific females over those of heterospecific females or pairs of either species. Female D. frontalis did
not discriminate among these frass categories, whereas female D. mesoamericanus preferred frass of conspecific
females. In gas chromatography–electroantennographic detection and gas chromatography–mass spectrometry
analyses, we determined that males of both species could sense a nearly identical spectrum of approximately
16 host- and beetle-produced compounds present in frass of females of one or both species. Only two of these
compounds, endo-brevicomin and ipsdienol, which were present in frass of female D. mesoamericanus and pairs of
either species but absent in frass of solitary D. frontalis females, qualitatively distinguished these categories. Several
known attractants and synergists for either species declined in concentration postpairing. Our results complement
earlier research and indicate how semiochemical composition and concentration in frass might mediate male
discrimination of attack sites of conspecific, unpaired females. Furthermore, our data indicate that semiochemical
responses for walking females differ from those of males and between species.
Keywords
syntopy, pheromone, electroantennogram, reproductive isolation, olfactometer
To read the full article please visit the link below:
Nino-Dominguez, Alicia, Brian T. Sullivan, Jose H. Lopez-Urbina, and Jorge E. Macias-Samano. 2018. “Discrimination of Odors Associated With Conspecific and Heterospecific Frass by Sibling Species Dendroctonus Frontalis (Coleoptera: Curculionidae: Scolytinae) and Dendroctonus Mesoamericanus (Coleoptera: Curculionidae: Scolytinae).” Environmental Entomology 47 (6): 1532–40. https://doi.org/10.1093/ee/nvy146.
