October 2022
Your Sting Ain’t So Hot

The eastern fence lizards (Sceloporus undulatus) are ant specialists, that displaying an ontogenetic shift in diet between the consumption of native and invasive ant species. These lizards have coexisted with the invasive red imported fire ant (Solenopsis invicta) since the ant’s introduction to the U. S., in the 1930s. Fire ants can pose a risk to the fence lizard, quickly moving from pray to predator as repetitive fire ant stings can cause paralyses and/or death. Young or small lizards are especially vulnerable to ant attack. Lizards have evolved longer legs that enable them to kick ants off, and adapted avoidance behavior such as rapid body twitching to throw off attacking ants before fleeing. There is also competition for nesting habitats, and ants will predate lizard eggs. A recent study however found that eastern fence lizards have yet another way to combat invasive fire ants.

Researchers found that lizards from areas with fire ants had a different immune profile than lizards from areas without fire ants. Immune profiles are critical for survival, and when a fire ant sting injects venom, it triggers an immune response. Researchers measured the innate immune system (which the lizards are born with) and the adaptive immune system (which the lizards develop after exposure to a foreign substance, such as an infection, or in this case, fire ant venom). To do this, they exposed lizards that are naïve to fire ants to ant venom through either stings or via consumption of dead fire ants. They found that when lizards were fed fire ants, the following three immune measures increased: basophils, complement activity, and immunoglobulin antibody (IgM). Basophils are a type of white blood cell. The complement system helps or complements antibodies. Immunoglobulin antibody (IgM) is reactive to fire ant venom. All three immune responses could potentially help the lizards survive a fire ant attack. The researchers believe that repeated exposure to the fire ant venom through consumption stimulates an increased immune response, like that of a vaccine. Field-caught lizards in areas with fire ants were found to have higher anti-fire ant antibodies and basophils when compared to those in areas without fire ants, suggesting this immune response may be the result of sub-lethal fire ant consumption. Not all lab results matched those observed in the field. Field-caught lizards are likely to have evolved adaptations or acclimated to repetitive fire ant exposure that affect immune function in ways not captured in lab experiments. Regardless, researchers concluded that the potential protective effects of sub-lethal consumption of fire ants may allow native lizards to better prepare for the lethal consequences of coexisting with fire ants. 

Read the research: Tylan et al., 2022



 eastern fence lizard at the Shawnee National Forest. Southern Illinois. Daniel Schewn. CC BY-SA 4.0Eastern fence lizard (Sceloporus undulatus) at the Shawnee National Forest, Southern Illinois. Credit: Daniel Schewn, CC BY-SA 4.0

lizard die from fire ant singsLizards can become paralyzed or die from repetitive fire ant (Solenopsis invicta) sings. Credit: Penn State.

immune response when eating antsEating fire ants causes an immune response similar to a vaccine that prepares lizards from lethal consequences from future fire ant bites. Credit: Penn State.

I Can Eat That

Burmese pythons (Python molorus bivittatus) are a popular exotic pet that has become an invasive and problematic species throughout Southern Florida. It seems like hardly a day goes by without hearing about another record-breaking python (18 feet) or how 231 invasive pythons were rounded up (way to go!), or that a cop answered a call to find an escaped python instead of a suspected water moccasin (thank goodness). But why are these snakes so problematic? One explanation is that these snakes can eat just about anything.

The Burmese python has evolved a larger gape (the amount the snake can open its mouth) that allows them to open and stretch their jaw enough to ingest prey six times larger than a snake similar in size. Since snakes swallow their prey whole, their gape is a key factor in determining what they can and cannot eat. The lower jawbones of snakes are not fused like a human's but instead loosely connected with an elastic ligaments that allow their mouth to open very wide. Pythons have an expandable jaw plus super stretchy skin between their lower jaw bones making their gape extra elastic. Over 40% of their average gape is from the stretchy skin.

Researchers measured different snakes and their potential prey to estimate the largest animals a snake could eat; with this they could then estimate the relative benefit of selecting different prey options. Data suggested that smaller snakes have more to gain from an enlarged gape that allows them to eat relatively larger prey. This gives them a wider range of prey and keeps them of the menu of predators. This supports why younger pythons are more successful than native species of the same size. In Florida, adult pythons can eat pray as large as deer and alligators.

Read the research: Jayne et al., 2022

jayne et al 2022Range of sizes used to determine maximal gape between Burmese python (Python molorus bivittatus) and brown tree snake (Boiga irregularis). Credit: Jayne et al., 2022

Jayne et al 2022 image 2CT scans showing the landmarks (dots) used for morphological measurements of Burmese python. Credit: Jayne et al., 2022

Where Did All My Friend Go?

Not all non-native species become successfully invasive once they are introduced to a new habitat. This is because not all introduced species become invasive, but also not all invasive species can create a successfully reproductive population, which classifies them as being established. There have been many studies to examine what make an invasive species successful at colonizing a new habitat. One explanation for this is the Enemy Release Hypothesis, which describes the advantage that is afforded to an invasive species when they lose their native predators upon being introduced to a new habitat. But a recent study examined the parallel of this to understand what factors prevent a successful introduction.

The Missed Mutualist Hypothesis is a notion that describes how invasive species leave behind their native mutualist, or species whose relationships provided them with a net for survival or reproduction. The loss of this relationship can inhibit an introduction, preventing invasive species from successfully invading a new range. Approximately 60% of introduced species fail to establish. The study observed that in plants introduced species interacted with two times as many “friendly” species, 2.3 times more often, in their native range compared to that of their invading range. Examining the species interactions between the native range vs. introduced range could continue to improve biocontrol and conservation methods.

However, sometimes when an introduced species successfully colonizes, it can become invasive because they have mitigated the loss of some or all their mutualists. Invasives adapt by making new “friendships” or undergo intense selection pressures to thrive without mutualists. When the later occurs, they tend to reallocate energy from mutualism toward an increase in competitive ability. When an invasive acquires a new mutualistic relationship, management tactics can be adopted to disrupt the novel interaction. Understanding both the positive and negative selection pressures that act on invasive species during the early stages of introduction and establishment could allow us to better understand the dynamics of colonization, and allow us to establish more robust prevention and management policy.

Read the research: Moles et al., 2022

Reminder: An invasive species is an introduced species that causes ecological, environmental, and/or, economic damage or harm. While introduced, non-native, exotic, or alien species are either neutral or beneficial with respect to other species. Both introduced and invasive species are known to become naturalized or fill niche spaces, but can still be harmful. Therefore, it is important to always examine the whole picture, the good and the bad, when facing a conservation issue. The ecosystem is a precious place with a delicate balance, and nothing should be introduced or removed without considering all of the consequences.

bee and flower copy
A mutualistic interaction between the European honey bee (Apis mellifera) and a flowering plant. Credit: Jon Sullivan, CC BY-SA 4.0

moles et al 2022 image 1 2Forest plots showing the number of interacting mutualist species or the frequency of mutualist interactions that were measured in the species’ native and introduced ranges. Credit: Moles et al., 2022

 moles et al 2022 image 2 2The effects of missed mutualisms, and pathways through which species can reduce negative effects. Credit: Moles et al., 2022

In Ancient Times

Usually when we think about invasive species, we are measuring the effects over a relatively short period of time. I’m talking decades or centuries, at the most. But researchers are now examining fossil records and geographic locations for evidence of species invasions that date back millions of years ago. A fossil invasion can be identified by mapping out species geographical ranges within the context of the evolutionary timeline. Any species that expands their geographical range during their lifetime, or in relation to their ancestral species, can be considered invasive. Observing ancient invasion events provide researchers insight invasive species have on ecosystem, structuring, extinction, and speciation from beginning to end with no human interference. They can also analyze invasive species ecological tolerances, broad geographic ranges, and higher-than-average survival potential during crisis interval. All this data can be applied to modern conservation methods. Until now, there was a gap in our observational abilities when studying invasion events. We could observe them over a short-term event (annual to decades) or long-term event (million plus year chunks).

New research presented at The Geological Society of America meeting showed that it is possible to study ancient invasions over a period of a few thousand years. The research focused on macrofaunal invertebrate fossils from the Clarksville Phase of the Richmondian Invasion, the first pulse of a biotic invasion that occurred during the Late Ordovician period around 450 million years ago. At that time, the area was a shallow sea but it is now northern Kentucky, southwestern Ohio, and southeastern Indiana. Community level changes were examined at very fine temporal level and related directly to changes in sea level and invasion arrival time. This research will bridge a gap in the fossil record, giving us a better understanding on how ancient invasions effected the area, that can be applied to modern invasions over a large time scale.

Read the research: Study of ancient invasive etc.

sediment layers
The sedimentary layers at Caesar’s Creek State Park, Ohio, record the post-invasion fauna. Credit: Alycia Stigall.

invasive fossil
The invader “horn coral” Grewingkia exposed in the post invasion Liberty Formation. Credit: Ian Forsythe.

Texas Citrus Need Your Help

The Asian citrus psyllid (Diaphorina citri) and the Citrus Greening pathogen (Candidatus liberibacter asiaticus) are threatening citrus in multiple Texas counties, and we need your help and samples to monitor the spread. This pest and pathogen are extremely detrimental to Texas citrus, both economically and agriculturally. The presence of either can greatly affect citrus yield.

TISI is offering diagnostic services if you suspect your backyard citrus has either the psyllid pest or the Citrus Greening pathogen.

Contact invasives@shsu.edu for instruction to send a plant or pest sample. If you are located within 200 miles of our headquarters, we can collect samples, and/or provide traps and monitoring services. Not only will we share the results and management strategies (where applicable), but you will become part of a multi-county monitoring survey that is striving to improve the health of Texas citrus!

Also Available: TISI offers educational workshops that highlight information about the Asian citrus psyllid, the pathogen Citrus Greening, and what you need to look out for in your own back yard. Your citrus can also become part of a TISI survey that is monitoring Texas citrus for pests and pathogens. If you are interested in this, TISI will providing trapping materials, assist with management strategies, and more.

symptoms of citrus greening. Jeffrey W. Lotz. Florida Department of Agriculture and Consumer Services. Bugwood.org
Symptoms of citrus greening bacterium. Credit: Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services, bugwood.org

citrus greening
Leaf mottle on grapefruit, a characteristic symptom caused by citrus greening bacterium but also seen on trees infected by Spiroplasma citri. Credit: J.M. Bove.

Biofouling Management for Recreational Boating Report published

Ever wonder why you are always being told to clean your boat, water craft, or water activity equipment? The GloFouling Partnerships has published a new Biofouling Management for Recreational Boating Report that can help answer all your questions. The aim of the report is to stop the spread of invasive aquatic species which can adhere to hulls and other areas of recreational craft by addressing how to manage biofouling. The report provides an overview of invasive aquatic species which are believed to have been introduced to different areas of the world through recreational boating. Current regulations and guidance are presented, as well as an overview of anti-fouling paints. Download the report: IMO Biofouling Management for Recreational Boating 2022.

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IMO Biofouling Management for Recreational Boating 2022.

Plant Party

The Plant Party webinar series is a collaboration between Texas Parks & Wildlife Department, USDA-Natural Resources Conservation Service, and Texas A&M AgriLife Extension Service. These quarterly webinars are meant to promote advanced training on all things plants, and to get people excited about the flora of our state. There are eight videos already posted and Plant Part #9 will post on December 21, 2022.

Click HERE to look through the video archive.

 plant party 
Plant Party. Credit: southtexasrangelands.tamu.edu

North American Invasive Species Management Association Training Webinars

This program is designed to provide the education needed for professionals and students who are managing or learning to manage invasive species. The courses include the most current invasive species identification, control, and management techniques, and how to comply with local and federal regulations.

Participants may register and enroll at any time, and will receive a certificate of invasive species management from NAISMA upon completion of the program.

All live webinars are open to the public. Recorded webinars are available to members of NAISMA.

NAISMA 2020 Webinar Schedule:

  • November 16, 1pm- Invasive mussel collaborative tools and accomplishments. REGISTER.
  • December 21, 1pm- Understanding ISPM 15 to reduce the risk of pests in wood packaging. REGISTER.
  • January 18, 1pm – Miller Creek Watershed Restoration: The value of partnership during a pandemic. REGISTER


Biocontrol Beats Back Brazilian Peppertree

According to a recent study, Brazilian peppertree thrips (Pseudophilothrips ichini) show promise as a biological control agent against populations of invasive Brazilian peppertree (Schinus terebinthifolia) in Florida. This species of thrips feeds exclusively on the leaves and stems of this species of peppertrees. Their feeding behavior reduces growth rate, plant height, and the production of leaves, green stems, fruit, and flowers. The study data showed that 60% of the thrips persisted in the survey sites for at least one generation after release, or for up to 60 days. This means that the thrips are showing signs of becoming a self-sustaining population. This is great news for other areas infested with Brazilian pepper trees, such as California, Hawaii, and Texas. In Port Aransas, TX, the CWMA is taking strides to start a biocontrol project using these trips to fight back against the ever-growing thickets of pepper trees in the area. This is the first biocontrol released for this invasive and plant researchers will continue to monitor and assess the progress and effectiveness, but so far, hopes are high.

Read the research: Wheeler et al., 2022


wheeler et al 2022 2
Pseudophilothrips ichini, (A) thrips orange larvae and (B) black adults aggregated on Brazilian peppertree (Schinus terebinthifolia) leaves at release site. Credit: Wheeler et al., 2022

Invasive Spotlight:

Poison Hemlock
(Callidiellum villosulum)

Poison hemlock (Conium maculatum) is a highly toxic plant that starts growing in the early spring. Itusually grows for 2 years, but in favorable locations it is a perennial. Its stems are ribbed and hollow with purple streaks or splotches and can grow 2-10 feet tall. The leaves are opposite and compound, with divided leaflets tapering into narrow segments which give it a fern-like appearance. The small white to yellowish flowers have five petals that bloom above the ovary. The flowers are borne in many umbrella-shaped clusters at the end of stalks. Underneath each cluster are 4-6 brown bracts (modified leaves). The fruit is a 2-3mm wide egg-shaped shell, with distinctive wavy ribs on the surface. It is made up of two dry halves that will eventually separate from each other. Each half contains a flat, ribbed seed. These seeds mature in August/September and are easily spread by mowing or agricultural equipment. Due to this, it is important to remove plants before seeds have reached maturity, usually between April and July (depending on the weather and area). Poison hemlock prefers shaded areas with moist soil but can be found along forest margins, roadsides, marshes and freshwater wetlands, disturbed sites, crop fields and meadows, and low-lying areas.

Poison hemlock is considered a twofold invader. Not only does it compete with native vegetation in pasture and crops land by quickly colonizing disturbed sites, but it poses a serious health hazard, as every part of the plant (leaves, stem, fruit, and root) are poisonous to livestock and humans. The plant contains highly poisonous alkaloids (coniine, g-coniceine, and related piperidine alkaloids) that put off a musty unpleasant smell. Sheep, cattle, horses, and other domestic animals are poisoned by eating small amounts of green or dried plant. Leaves are poisonous in the spring, up to the time the plant flowers. However, fresh leaves are unpalatable, so livestock are less likely to eat it if other food is available. People have also been poisoned by eating poison hemlock. Usually, the poisoning occurs because hemlock root was confused with wild parsnips, hemlock leaves with parsley, or hemlock seed with anise. Whistles made from hollow hemlock stems have caused deaths in children. In many placed this plant has been listed as a Federal Noxious Weed.

Poison hemlock is now present in most of the U. S. It requires active control measures to prevent a total infestation. Manual and chemical management options are often deployed before the seeds mature, but there is also a biocontrol option. The European palearctic moth (Agonopterix alstroemeriana) have been spread throughout the U.S. and New Zealand. The larvae can cause severe almost complete defoliation along leaves, young stem tissue, flowers, and seeds.

There are many lookalikes: wild carrot (Daucus carota), wild parsnip or wild cow parsnip (Pastinaca sativa), and water hemlock (Cicuta maculata). Wild carrot and wild parsnip have white umbrella-shaped flower clusters, but they do not have purple mottling on their stems. In addition, wild carrot has a hairy stem while wild parsnip has a ribbed stem. Water hemlock does have purple mottling and hairless stems, but unlike poison hemlock, it has a cluster of fleshy taproots at the base.

For more information about the poison hemlock, visit the TexasInvasives species info page. Safety precautions should be deployed when dealing with poison hemlock!

poison hemlock whole plant
Poison hemlock (Conium maculatum). Credit: Joseph M. DiTomaso, University of California - Davis, bugwood.org

 purple splotches along stem of poison hemlock 
Characteristic purple splotches along stem of poison hemlock. Credit: Joseph M. DiTomaso, University of California - Davis, bugwood.org

poison hemlock seeds
Poison hemlock seeds. Credit: Ken Chamberlain, The Ohio State University, bugwood.org

Map Database of Vascular Plants of Canada.
Map depicting distribution of poison hemlock throughout U.S. Credit: Brouillet et al., 2006


Get Involved Today!!

The Texas Invasive Species Institute (TISI) and The Texas Research Institute for Environmental Studies (TRIES) have many surveys and projects underway. These facilities strive to provide yearly invasive species presence and absence data to the authorities. Pre-screening is one of the first lines of defense in the war against invasives. However, sometimes it is hard to do it alone.

With the aid of the public and citizen scientist, we could cover a much wider area, and gather a more substantial amount of data. When it comes to protecting our environment, there is an opportunity for everyone! Together we can make a difference, one research project at a time.

See how you can get involved by reading the projects listed below or see all the available projects on the Texas Invasives website HERE.

Aquarium Watch: Looking for Prohibited Invasive Aquatic Species

Please help texasinvasives.org and natural habitats by looking for 14 prohibited invasive aquatic species being sold in your local aquarium store. With just one photo you can assist us in finding and documenting which stores are selling prohibited species. Texasinvasives.org will contact the appropriate Texas institutions to remove the species for sale.

If you would like more information please email invasives@shsu.edu, and mention you want to assist with our Aquarium Watch.

Air Potato Survey

Help Texas Research Institute for Environmental Studies conduct an air potato survey by actively reporting any infestations seen in your area. The air potato (Dioscorea bulbifera) is a fast growing, high climbing vine. Potato-like tubers are the primary means of reproduction for this vine. They can be as small as a marble or as large as a softball. Native yams are often confused for air potatoes, to avoid this confusion please refer to the key below:

- Plants rhizomatous; bulbils never produced in leaf axils; petiole base never clasping the stem; Native D. villosa
- Plants tuberous; bulbils produced in leaf axils; petiole base sometimes clasping the stem; Invasive D. bulbifera

For additional information, please refer to the TexasInvasives information page.

If you believe you have identified an air potato vine, please email invasives@shsu.edu and include the following information: an image, an approximate number of vines present, the location (including whether it is on public or private land), and if bulbils are present (the potato-like tubers that emerge from the stem).

Participation opportunities
Participation Opportunities. Credit: KNKleiner, TRIES.

Armorded catfish. Photographer United States Geological Survey
Armored catfish (Hypostomus plecostomus). Credit: United States Geological Survey.

air-potato (Dioscorea bulbifera)2 bulbil. credit Karen Brown
Air-potato (Dioscorea bulbifera), bulbil emerging from leaf axil. Credit: Karen Brown.

More News

Pflugerville Water Treatment Plant to Expand After Being Damaged by Invasive Zebra Mussels
Many bodies of water in Travis County are infested with invasive zebra mussels (Dreissena polymorpha), including Lake Pflugerville, in Pflugerville, TX, which has been infested since 2019. This infestation has resulted in damage to the city’s water treatment plant. Plans for an upgrade are underway. kxan.com

Bucking Convention to Track the Upside of Invasive Species
Some scientists want to document the positive impacts of alien species. The development of the EICAT+ system is helping that happen. However, this topic has been a hotbed for debate for a long time and some scientists think it is a waste of time and resources. What do you think? undark.org

Candy-Looking Creature Spotted Along San Antonio River Walk
The egg casings laid by female apple snails (Pomacea maculate) have a vague resemblance to pink bubble gum. These snails and egg casings can often be seen along the rocks of the San Antonio River Walk. The article contains contact information if you ever see these snails in San Antonio. mysanantonio.com

Supply Chains Must Mitigate Threat of Invasive Species, For All Our Sakes
International trade is a big contributor to the spread of invasive species. Members of the United Nation’s Food and Agriculture Organization (FAO) are working together to find a solution for invasive pest problem, whether it be a new container design or the mitigation of different steps throughout the shipping process from start to finish. theloadstar.com

Warning: Firewood Could Carry Invasive Insects
Untreated firewood can be infested with invasive insects, and it is often difficult to tell whether or not your wood is infested before you buy it or move it. This article may be about Virginia forests, but the same information applies to Texas forests and firewood. whsv.com

Grapevines May Only Need Help to Survive Heavy Spotted Lanternfly Infestations
Grapevines infested by a low-to-medium population density of spotted lanternflies (Lycorma delicatula) suffer minimal effects. Researchers also looked at grapevine-lanternfly interactions, how feeding effects the plant, and if feeding had cumulative effects. phys.org

Invasive Stink Bug Habitat Could Expand with Climate Change
A recent study found that changing weather could increase suitable habitat for the brown marmorated stink bug (Halyomorpha halys) in the U.S. by 70%. It is proposed that there will be a northward shift effecting the Mid-Atlantic and a westward shift effecting the West coast. news.wsu.edu

Lizards With 'Outgoing' Personalities Are Better Invaders
The delicate skink (Lampropholis delicata) is the only Australian lizard to become invasive overseas. Upon comparing the behavior of different lizard populations across invasive vs. native ranges, researchers noticed that the invasive skinks were bolder. phys.org

Best Way to Estimate Costs for Invasive Plant Removal? Get Out and Dig
A group of researchers grew plots of invasive plants so they could calculate how much it would cost to remove them, taking into consideration regrowth, repeat treatments, and dispersal. phys.org

Meet The Parasitoid Wasps Scientists Hope Will Save (Some) Of Vermont's Ash Trees
Like many other places in the U.S., Vermont’s forests are suffering from the presence of the invasive emerald ash borer (Agrilus planipennis). However, three tiny parasitic wasp species are providing foresters with a little bit of hope as they release over thousands of the biocontrol agents onto infected ash trees. capeandislands.org


Sentinel Pest Network and Invaders of Texas Workshops

Invaders of Texas workshops train volunteers to detect and report invasive species as citizen scientists. Workshops, which are free, are designed to introduce participants to invasive species and the problems they cause, cover aspects of invasive species management, teach identification of local invasive plants, and train participants to report invasive plants using the TX Invaders mobile application. The workshop is 7 hours long (usually on a Saturday, but scheduling is arranged with each individual host group). The workshop satisfies Master Naturalist training requirements.

Sentinel Pest Network workshops serve to increase the awareness and early detection of a set of particularly important invasive species to help prevent their spread into Texas or their further spread within Texas. Participants learn to identify species such as the Emerald Ash Borer, Cactus Moth, Asian Longhorned Beetle, and other pests of regulatory significance, and to report them. The workshop is 3.5 hours long. The workshop satisfies Master Naturalist training requirements.

Upcoming Workshops: