Reduced Intraspecific Variation in Foliar Micro and Macronutrients among Quercus Garryana Trees in the Expanded Range May Contribute to Outbreaks of a Range Expanding Insect

Due to the effects of rising global temperatures and the abrupt changes in ecosystems, phytophagous insects are expanding their ranges poleward. An oak gall wasp,Neuroterous saltatoris, has expanded its range from mainland North America to Vancouver Island, British Columbia, and is outbreaking in its expanded range causing damage to its host plants Quercus garryana. Q. garryana has reduced genetic diversity with decreased intraspecific variation towards the poles. This research group collected leaves from trees that ranged from low to highly infested. Leaves were dried and ground and levels of macronutrients and micronutrients were measured. Higher intraspecific variation in nutrients were found among trees in the native compared to the expanded range, which may underlie patterns of higher patchiness of N. saltatorius-infested trees in the native range. It was also determined what nutrients are influencing the infestation of N. saltatorius.https://orb.binghamton.edu/research_days_posters_2024/1141/thumbnail.jp

Biogeographical Patterns in Oak Gall Wasp-Parasitoid Communities Associated with Oregon White Oak, Quercus Garryana, Under Anthropogenic Change

Species are expanding their ranges poleward as a consequence of global climate change. However, natural enemies may lag behind range-expanding hosts, facilitating “ecological release.” A species that has experienced a recent poleward range expansion is Neuroterus saltatorius, an oak gall wasp (Hymenoptera: Cynipidae) that expanded its range from mainland western North America to Vancouver Island, BC. In its expanded range, it is threatening oak savanna ecosystems. This species induces gall structures on its host plant, Quercus garryana. Parasitoid wasps are attracted to galls and feed on developing insects in galls, acting as population control agents. We examine how interactions with enemies and competitors change over the range of Q. garryana and in the native and expanded range of N. saltatorius, and if changes in interactions relate to ecological release. Parasitoid wasps were reared from cynipid species collected from Q. garryana at 18 sites from Northern California to Vancouver Island, BC and identified to morphospecies using taxonomic keys. We found 21 cynipid morphospecies that co-occur with N. saltatorius on Q. garryana throughout its range, with a subset of cynipids (9 morphospecies) in the expanded range. We have identified 16 species of parasitoids from N. saltatorius. Preliminary results suggest a different composition of parasitoid enemies in its expanded range compared to its native range. This is likely due to a change in the composition of known generalist parasitoids that attack the range-expanding host that may not be effectively switching other from other competitors, rather than from a loss of known specialist parasitoids. We have also identified parasitoid morphospecies from a co-occurring competitor cynipid, Andricus quercuscalifornicus, and found no overlap in parasitoids with N. saltatorius. This suggests that A. quercuscalifornicus is not a competitor and does not contribute to the release of N. saltatorius. Uncovering how species interactions with range-expanding hosts are altered is important to predict outcomes of anthropogenic range expansions.https://orb.binghamton.edu/research_days_posters_2021/1085/thumbnail.jp

Detecting Apparent Competition by Shared Parasitoid Enemies between a Native and a Range-Expanding Oak Insect

The expansion of a species’ range due to anthropogenic change leads to changes in species interactions with cascading effects in ecosystems. Oak gall wasps and their parasitoid enemies are a diverse community of insects that are structured by a network of interactions. One important interaction is “apparent competition,” in which a gall wasp species can indirectly compete with another species through shared parasitoids. Neuroterus saltatorius, an oak gall wasp, is experiencing a range expansion on the west coast of North America, where it outbreaks and causes damage in oak ecosystems. A co-occurring oak gall wasp, Andricus opertus, shares its range with N. saltatorius. We describe the parasitoid community of A. opertus to see if it is an apparent competitor to N. saltatorius. We have identified 32 morphospecies and are performing DNA barcoding to more accurately uncover interactions between parasitoids and the two host oak gall wasp species.https://orb.binghamton.edu/research_days_posters_2022/1094/thumbnail.jp

The Role of Apparent Competition in Facilitating Ecological Release of a Range-expanding Insect

Due to anthropogenic climate change, species are expanding their historical natural ranges. However, interacting species will not shift synchronously and range-expanding species are likely to lose interactions and pick up novel ones in their expanded range. If antagonistic interactions, such as with competitors or enemies are lost, range-expanding species may experience “ecological release” and have impacts in their expanded range. Of the parasitoid wasps that attack phytophagous insects, some are specialists and some are generalists attacking alternative hosts (competitors). Range-expanding species may lose enemies if their specialists fail to follow from their native range and if generalist enemies fail to switch from competitors in the expanded range (“release from apparent competition”). We study a poleward range-expansion of a phytophagous gall-forming insect Neuroterus saltatorius that expanded its range from mainland western North America to Vancouver Island, BC, where it is outbreaking on its plant Querucs garryana. N. saltatorius co-occurs with several other gall-formers on its host, including Andricus opertus, throughout its native and expanded range. Here, we ask if A. opertus acts as an apparent competitor (shares enemies) with N. saltatorius, and if apparent competition is weaker in the expanded range. These two host species were collected from 18 sites that span the range of Q. garryana. We reared parasitoid wasps from them and identified parasitoids to morphospecies using taxonomic keys. We identified 16 parasitoids from N. saltatorius and 39 from A. opertus. Of these, 13 species of parasitoids are shared between the two host species in all regions, and we will calculate the rate of shared overlap to see if there are fewer shared species in the expanded range. This result would suggest that release from apparent competition contributes to ecological release. Understanding how biotic interactions change under range expansions is important to predict species responses to climate change.https://orb.binghamton.edu/research_days_posters_2021/1095/thumbnail.jp