ASSESSMENT OF INVASIVENESS AND ECOLOGICAL IMPACT
An documented account of 812 non-native species reported to grow outside of cultivation in Texas has been developed. About 300 of these have been reported since the 1970 publication of the Manual of the Vascular Plants of Texas, and each of the latter taxa has been documented by at least a literature reference. A “Fundamental Invasiveness Index” provides a framework for assessment and ranking of each of the non-native species according to their invasiveness and ecological impact. The Index is based on knowledge of the species from field, herbarium, and literature, according to the following criteria. F1: Invasive in both disturbed and natural habitats, negatively affecting native species or natural biodiversity by altering native
vegetation and habitats or by outcompeting or hybridizing with native species; or, invasive into agricultural habitats and causing signifi-cant economic damage; including woody, herbaceous, and aquatic species. F2: Abundant in number and widespread, commonly invasive in disturbed habitats, much less commonly in natural habitats;
subdivided into woody, herbaceous, and aquatic species. F3: Relatively few in number, known from relatively few localities, usually in disturbed habitats; subdivided into woody and F4: Status unknown.
Numbers of species per category are F1-Woody, Herbaceous, and aquatic (51), F2-Woody (13), F2-Herbaceous (228), F2- aquatic (16), F3-Woody (76), F3-Herbaceous (348), and F4 (80). A Watch List includes 52 woody, herbaceous, and aquatic species most likely to warrant F1 ranking.
Se realiza un informe documentado de 812 especies no nativas que crecen fuera de cultivo en Texas. Unas 300 de ellas se han citado desde la publicación en 1970 del Manual of the Vascular Plants of Texas, y cada uno de estos últimos taxa se ha documentado con al menos una referencia bibliográfica. Un “Fundamental Invasiveness Index” ofrece un marco para la evaluación y ordenación de cada una de las especies no nativas de acuerdo a su potencial invasor e impacto ecológico. El índice está basado en el conocimiento de las especies en el campo, herbario, y bibliografía, de acuerdo a los siguientes criterios. F1: Invasiva tanto en hábitats modificados y naturales, que afecta negativamente a especies nativas o a la biodiversidad natural por
alterar la vegetación nativa y hábitats o por competir o hibridar con especies nativas; o, invasoras en hábitats agrícolas causando daños económicos importantes; incluyendo especies leñosas, herbáceas, y acuáticas. F2: Abundantes en número y extendidas, generalmente invasivas en hábitats alterados, mucho menos en hábitats naturales; sub-
divididas en especies leñosas, herbáceas, y acuáticas. F3: Relativamente pocas en número, conocidas de relativamente pocas localidades, usualmente en hábitats alterados; subdivididas F4: Estatus desconocido.
Los números de especies por categoría son F1-leñosas, herbáceas, y acuáticas (51), F2-leñosas (13), F2-herbáceas (228), F2-acuáticas (16), F3-leñosas (76), F3-herbáceas (348), y F4 (80). Una lista visual incluye 52 especies leñosas, herbáceas, y acuáticas que probablemente justifican una situación en F1.
About 516 non-native species were known 40 years ago to occur outside of cultivation in Texas (as counted from Correll & Johnston 1970)—about 11 percent of the total flora of the state at that time. Since that time, about 300 additional introductions to the state have been reported in various publications (summarized in the PLANTS Database: USDA, NRCS 2009; the PLANTS Database has drawn its information from a variety of sources, including major publications on the Texas flora). The present paper provides a summary account of the currently known non-native Texas flora, with documentation for those species included in
J. Bot. Res. Inst. Texas 3(2): 971 – 991. 2009 Journal of the Botanical Research Institute of Texas 3(2)
the account since 1970 and a ranking of invasiveness and ecological impact for each species included. The system presented here is simple enough to allow a quick assessment of a large number of species but still to provide a fundamental overview of each species.
Various lists of invasive species have been developed for Texas, but documentation for these lists is not
readily available. The most comprehensive list is presented by TexasInvasives.org (2009), which includes 139 species, with a photo for each and a listing of the family, common name, duration, habit, and information on morphology, biology, and distribution, including links to detailed Texas maps. Two lists have state-wide legal standing: the Noxious Plant List of the Texas Department of Agriculture (TDA 2009) with 29 species and a list of Prohibited Exotic Species from the Texas Parks and Wildlife Department (TPWD 2009) with 19 aquatic species. The list of 13 aquatic species from the North Texas Water Garden Society (NTWGS 2009) appears to be a subset of the TDA list. The City of Austin lists 26 species (some listed simply as the genus) of Invasive Plants to Avoid (Austin City Connection 2009).
The Invaders of Texas (2009) program organizes teams of local citizen scientists who seek out and
report occurrences of invasive species. This is a very useful program, both practically and scientifically—as of May 2009, more than 7400 detailed field observations have been reported and are available online. Each field report includes precise locality information (with coordinates automatically mapped), an indication of abundance at the locality, and usually a photo of the plant or populations taken at the site of observation. The target species sought by the Invaders of Texas participants are the 139 on the TexasInvasives.org list (2009). For each species, individual field observations are mapped in aggregate to show their total distribu-tion in the state. non-native species in texas—development of a list and documentation. A preliminary list of non-native species in Texas was developed by the author from the PLANTS Database (USDA, NRCS 2009), using an Advanced Search for Texas taxa introduced to the Lower 48 states. Journals and other literature were reviewed for possible additions, and a number of species have been excluded. Identifications in the Texas list presented here often are not made to infraspecific rank (in contrast to the PLANTS list), because vouchers commonly have not been examined or because the validity of the infraspe- cific taxonomy is not clear. Only plants that are naturalized have been included (vs. cultivated or persisting from cultivation), though some on the list probably would best be characterized as waifs (Nesom 2000) if follow-up observations were done at sites where they were reported to occur. Whether or not a species is native sometimes may be difficult to judge—generally such instances are discussed in the documentation for the full list (Nesom 2009a).
Documentation for the occurrence of these species in Texas (Nesom 2009a) begins with literature and
other records that have been published mostly after 1970, the date of publication of Correll and Johnston’s “Manual of the Vascular Plants of Texas,” which remains the primary floristic resource for the state. In the course of assigning invasiveness rankings, however, the rationale for inclusion of each species on the full list has been examined. For species included in the documentation, at least one full literature reference is provided, with reported Texas counties and other brief notes on the status of the species, as appropriate or as known. Many taxa on the PLANTS list or from elsewhere have been excluded from the Texas flora because of mistaken or faulty documentation (Nesom 2009b for examples from the Asteraceae), and these are specifically noted in the commentaries (Nesom 2009a). A number of species have been reported simply by listing (Johnston 1990; Hatch et al. 1990) or by mapping (Turner et al. 2003); vouchers or other docu-mentation for these are being provided.
Documentation for the full list of non-native taxa is an essential and critical part of both this process
and this report. Because the information is complex and completion and supplementation are ongoing, it remains as an online resource (Nesom 2009a). Addition of voucher information and other documentation for species first reported in lists by Johnston (1990) and Hatch et al. (1990) and elsewhere will be a significant advance. Nesom, Fundamental invasiveness index for non-native species of Texas systems for assessment and ranking of invasiveness. In developing a protocol for evaluating Texas non-native species for invasiveness and ecological impact, a representative set of other systems toward the same end has been considered and studied. * Alien Plants Ranking System (Ver. 5.1) (APRS Implementation Team 2000) * Ranking Invasive Exotic Plant Species in Virginia (Heffernan et al. 2001) * Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands (Warner et al. 2003) * An Invasive Species Assessment Protocol: Evaluating Non-native Plants for Their Impact on Biodi- * Invasiveness Ranking System for Non-native Plants of Alaska (Carlson et al. 2008) * New York State Plant Ranking System for Evaluating Non-Native Plant Species for Invasiveness
Perhaps the most widely applied (and adapted) of these is Morse et al. (2004), developed by NatureServe, in collaboration with The Nature Conservancy and the U.S. National Park Service. It is a “protocol for as-sessing and categorizing non-native plants according to their impacts on native biodiversity.” NatureServe Explorer now includes an impact rank (“I-rank”—high, medium, low, or insignificant) for many non-native plant species of the USA.
In each of the systems above, assessment and ranking of an individual species invokes a series of detailed
questions grouped into a set of topics, usually including some or all of these:
* ecological impact and potential for future impact; * biological attributes, including dispersal ability and invasiveness potential; * ecological amplitude; * geographic extent of invasion; and * control/management feasibility and cost.
A significant amount of the information required for the ranking criteria is drawn from literature pertinent to the species under consideration. After scoring is complete for the whole set of questions, the species may be ranked numerically by its additive score, or the additive score may translate to a broader category.
The ranking protocol for the Tennessee Invasive Exotic Plant List (Tennessee EPPC 2001) is consider-
ably different from those above. In the Tennessee system, a species is assigned by a committee of biologists to one of the following categories (the number of Tennessee species in each category is indicated): rank 1—severe threat: Exotic plant species that possess characteristics of invasive species and spread easily
into native plant communities and displace native vegetation. (29 species)
rank 2—significant threat: Exotic plant species that possess characteristics of invasive species but are not
presently considered to spread as easily into native plant communities as those species listed as Rank 1. (49 species)
rank 3—lesser threat: Exotic plant species that spread in or near disturbed areas; and are not presently
considered a threat to native plant communities. (28 species)
Watch list a—Exotic plants that naturalize and may become a problem in the future; includes species that
are or could become widespread in Tennessee. At this time more information is needed, and there is no consensus about their status. (24 species)
Watch list B—Exotic plant species that are severe problems in surrounding states but have not been reported
The protocol proposed here for Texas non-native species is very similar to the one developed for Tennessee. Invasiveness and ecological impact of texas non-native species. The system outlined here for use in Texas emphasizes simplicity, allowing assessment of the large number of non-native species (all that are known to occur in the state). Because essential elements of biology and geography are included in the assessments, the system is termed the Fundamental Invasiveness Index. After becoming familiar with the categories of the index and the characteristics of the species under consideration, the species is assigned to one of the categories. The first category (F1) applies to species that have invasive biological characteristics as well as a strong and adverse impact on natural systems and biodiversity (or an adverse economic impact). The other two main categories (F2, F3) include species that are less significant Journal of the Botanical Research Institute of Texas 3(2)
in ecological or economic impact, with the division between species of F2 and F3 made on the basis of their geographic distribution, abundance, and potential for spread. Within F2 and within F3, slightly dif-ferent characterizations are given for woody and herbaceous species, as the two growth forms are generally distinct in biology.
The biology of aquatic species is distinct from terrestrial ones, in part because of their potential for
extremely rapid dispersal in local aquatic systems. Emergents that grow in open water—sometimes per-sisting in mud flats or in periodically wet habitats (i.e., Alternanthera, Ludwigia, Nasturtium)—are included as aquatics. Each species has the potential to cause major ecosystem damage, and many of them already are recognized as noxious over wide regions; others are ecologically damaging at least locally in the lake or stream where they occur. Somewhat arbitrarily, aquatic species are recognized here in the category of maxinum negative effect if they occur in 10 or more counties (as recorded by herbarium voucher specimens, expert sightings or photos, or other reliable documentation). Hydrilla verticillata is vouchered by specimens at TEX for only about six Texas counties but clearly occurs more widely (as do some of the other species). Otherwise, aquatic species known to occur in 9 or fewer counties all are placed in the same category.
A ranking system such as that from NatureServe provides assessments based on array of explicit and
detailed criteria. For Texas and its large number of non-native species, contemplation of such an intricate system and the massive amount of time required for its completion perhaps has inhibited even the begin-ning of one. The system here, however, appears to provide a realistic overview of the situation in Texas, even though many assessments remain to be clarified for species currently included. Further, the current account at least provides a basis from which more detailed assessments may be developed.
For accurate evaluation of an individual species, knowledge is required of the following. * nativity. Is the species native or non-native? * approximate date of introduction in texas (e.g., pre-1970, 1970s, 1980s, 1990s). Documentation in the current system does not provide specific information for species introduced before 1970 (those in- cluded in Correll & Johnston’s Manual of the Vascular Plants of Texas), but for species recorded since that time, dates are evident, as much as possible, in a review posted and periodically updated on the internet (Nesom 2009a). * Current geographic distribution. Based on distribution maps in Turner et al. (2003), distribution maps generated by data from Invaders of Texas (2009), records from herbaria (primarily those in Texas), and literature. * Ecological/reproductive behavior in texas and in other regions. Based on field experience of the author and others, published literature, information from herbarium collections. * Basic habitat and growth form (aquatic or terrestrial, herbaceous or woody). Based on field experi- ence, published literature, information from herbarium collections.
F1—Invasive in both disturbed and natural habitats. Negatively affecting native species or natural biodiversity by altering native vegetation and habitats or by outcompeting or hybridizing with native species; or, invasive into agricultural habitats and causing significant economic damage. Aquatic species known to occur in 10 or more counties. Woody, herbaceous, and aquatic species. Examples: Arundo donax, Bothriochloa ischaemum var. songarica, Centaurea melitensis, Eichhornia crassipes, Ligustrum sinense, Lonicera japonica, Lygodium japonicum, Nandina domestica, Salvinia molesta, Sorghum halepense, Triadica (Sapium) sebifera, Ulmus pumila. F2—Abundant in number and widespread, commonly invasive in disturbed habitats, much less commonly in natural habitats (Table 1). F2-Woody—Trees, shrubs, subshrubs, and woody vines. Abundant in number and widespread, commonly invasive in disturbed habitats
such as roadsides, fencerows, woods edges, and others, sometimes potentially or incipiently damaging in natural habitats (as F1). Examples: Albizia julibrissin, Morus alba, Nicotiana glauca, Poncirus trifoliata, Pyrus calleryana,Vitexagnus-castus. F2-Herbaceous—Annual and perennial herbs and grasses. Known invasive and/or clearly expanding in geographic range, primarily in
lawns, roadsides, and other open, disturbed habitats, sometimes in croplands, widespread and usually abundant but often produc-
Nesom, Fundamental invasiveness index for non-native species of Texas
Table 1. Numbers of non-native species in Texas ranked as F1, F2, F3, and F4. The total is 812 species. Herbaceous
ing relatively little biomass. Not significantly affecting native species or natural biodiversity or otherwise strongly altering native vegetation and habitats. Examples: Avena sativa, Bellardia trixago, Coronilla varia, Daucus carota, Duchesnia indica, Erodium cicutarium, Galium aparine, Gamochaeta coarctata, Hypochaeris microcephala, Lamium amplexicaule, Medicago lupulina, Stachys floridana, Stellaria media, Taraxacum officinale, Torilis nodosa, Trifolium repens, Veronica arvensis, Vicia sativa.F2-aquatic—Aquatic species known to occur in 1 to 9 counties. F3—Relatively few in number, known from relatively few localities, usually in disturbed habitats. F3-Woody—Trees, shrubs, subshrubs, and woody vines. Relatively few in number, known from relatively few localities, usually in disturbed
habitats, repeatedly introduced or perhaps merely long-persisting at some localities, not showing aggresively invasive tendencies, or perhaps incipiently invasive. Examples: Ardisia crenata, Buddleja lindleyana, Cinnamomum camphora, Hibiscus syriacus, Koelreuteria elegans, Manihot esculenta, Photinia serratifolia, Pistacia chinensis, Pyracantha koidzumii, Pyrus communis, Rosmarinus officinalis.F3-Herbaceous—Annual and perennial herbs and grasses. Occurrence outside of cultivation known from only one or a few populations,
usually in disturbed habitats. Apparently showing little or no increase of abundance or geographic range since the initial report. Examples: Cichorium intybus, Gomphrena globosa, Phyllanthus fraternus, Plantago coronopus. Or in some species, sporadically appearing from repeated introductions and not reproducing. Examples: Citrullus lanatus, Consolida orientalis, Ipomoea batatas, Luffa aegyptiaca, Narcis-sus pseudonarcissus, Tagetes erecta.F4—Status unknown. Watch list: terrestrial non-native species in texas potentially ranked as F1. Many of the non-native species in Texas occur only in small areas. Among these are a significant number that have been relatively recently recorded for the state and that are known to be both highly invasive and ecologically destructive in other regions of the United States. These features characterize the species included on the Texas “Watch List” (Appendix 5). These species may be expected to spread in Texas and become ecologically problematic. Some of the woody species, like Cinnamomum camphora, Photinia serratifolia, Pista- cia chinensis, and Vitex agnus-castus are widely planted and seeds often are nearly ubiquitous around urban areas—each of these species already appears to be spreading into natural habitats. In contrast, species such as Albizia julibrissin and Morus alba are invasive and occur in large numbers but appear to be more restricted to disturbed habitats or to edges of woods.
An interesting point regarding pantropical maritime species potentially or incipiently invasive in Texas
has been raised by Tom Patterson (South Texas College, Rio Grande City). “How to classify these new arrivals? For the most part, they have not escaped from cultivation. But they potentially are a threat and I believe they need their own category. After tropical storms South Padre Island receives sea beans, red mangrove fruits, and coconuts. Some of these propagules in the past have produced plants and have been infrequently documented by collections, only later to succumb to a severe freeze. With global warming more of these pantropical maritime species will persist and become naturally adventive to Texas.” In this category Patterson includes Caesalpina bonduc, Canavalia rosea, Cassytha filiformis, Conocarpus erectus, Laguncularia racemosa, Rhizophora mangle, and Scaveola plumieri. These are added as a special category in the Watch List (Appendix 5). roadside flora. The emphasis here on ecological impact to natural habitats is especially significant in Texas, where such a relatively small portion of the land is unaltered and it is critical to protect remaining natural areas. Following Journal of the Botanical Research Institute of Texas 3(2)
that thought, however, roadsides in Texas are exceptionally significant since they comprise a significant por-tion of public land in the state and in some places are important in harboring elements of the native flora.
“It’s hard to know what to do with roadsides. They’re not entirely natural, and sometimes the weediness
stops at the fence. Don’t you wish you had a time machine and could go back 1000 years (or 100) and see Texas without all of the exotics? I wonder what spring would look like without all the non-native mustards, mints, beans, grasses, etc. What might we have had that is no longer here at all? All that vetch and clover and henbit and shepherd’s purse had to replace *something*” (Monique Reed, pers. comm.).
All non-native species known to occur in Texas, with “Fundamental Invasiveness Index” rankings. Species on the “WATCH List” (Appendix 4) are indicated. ACANTHACEAE Cuminum cyminum L.—F3-Herbaceous Hygrophila polysperma (Roxb.) T. Anders.—F2-Woody Cyclospermum leptophyllum (Pers.) Sprague ex Britt. & Nomaphila stricta (Vahl) Nees—F2-Woody
Wilson—F2-Herbaceous Ruellia caerulea Morong—F3-Herbaceous
syn= Apium leptophyllum (Pers.) F. Muell. ex Benth. Daucus carota L.—F2-Herbaceous Thunbergia alata Bojer ex Sims—F3-Herbaceous Foeniculum vulgare P. Mill.—F3-Herbaceous ALOACEAE Hydrocotyle sibthorpioides Lam.—F3-Herbaceous Aloe vera (L.) Burm. f.—F3-Herbaceous Pastinaca sativa L.—F3-Herbaceous Petroselinum crispum (P. Mill.) Nyman ex A.W. Hill—F3- AMARANTHACEAE Herbaceous Achyranthes aspera L.—F3-Herbaceous Alternanthera caracasana Kunth—F2-Herbaceous Scandix pecten-veneris L.—F3-Herbaceous Alternanthera philoxeroides (Mart.) Griseb.—F1-Woody Torilis arvensis (Huds.) Link—F2-HerbaceousWATCH Alternanthera pungens Kunth—F3-Herbaceous Torilis nodosa (L.) Gaertn.—F2-Herbaceous Alternanthera tenella Colla—F3-Herbaceous
280 Case report Vlaams Diergeneeskundig Tijdschrift, 2010, 79 Estrogen-induced pancytopenia due to a Sertoli cell tumor in a cryptorchid Beauceron Oestrogeengeïnduceerde pancytopenie door een sertoliceltumor bij een 1 H. De Bosschere, 2 C. Deprest 1 Medisch Labo Bruyland – Afdeling Diergeneeskunde, Meiweg 1, B-8500 Kortrijk, Belgium2 Dierenartsenpraktijk Deprest, Verlovestraat 4,