Papers by Justin Williams
A new species from Honduras, Tintinnabularia murallensis, is described and illustrated. The new s... more A new species from Honduras, Tintinnabularia murallensis, is described and illustrated. The new species broadens the current circumscription of the genus. An illustration of the new species is provided, as is a distribution map for all recognized species of the genus.
HortScience, 2005
The state of Texas consists of roughly 4800 species of vascular plants. In 1970, it was estimated... more The state of Texas consists of roughly 4800 species of vascular plants. In 1970, it was estimated that 200 of these were introduced species. By 2003, the number of introduced species almost doubled to 350. Using the Atlas of the Vascular Plants of Texas, a database was compiled listing the invasive species in Texas and which of the 254 counties they inhabited. This database was then converted into a GIS platform that allowed us to analyze those data spatially. With these data, we were able to calculate the actual number of invasive species per county. In addition, these data were used to predict possible points of invasive species introduction, the rate of spread for certain problematic species, routes of migration, and to isolate counties under threat of possible infestation.
Gryllotalpidae, or mole cricket, is a family of burrowing Orthoptera with a highly sclaritized pr... more Gryllotalpidae, or mole cricket, is a family of burrowing Orthoptera with a highly sclaritized pronotal thorax and a pair of specially modified digging fore legs. The fossorial fore legs play a important role in the construction and maintenance of burrows that allow for amplification of sound/calls and food scavenging along grass root systems. We propose that due to the degree if sclaritization and hardening of the fossorial fore legs that metal composites will be found along the cutting edges. We will be using Scanning Electron Microscopy (SEM) with X-ray microanalysis or Energy-dispersive X-ray spectroscopy (EDS) to look for the presence of metal composition. Our focus will be on species along the southern and eastern gulf coast.
Lundellia, 1999
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
The abaxial leaf surfaces of Fraxinus in the southwestern USA and northwestern Mexico are sometim... more The abaxial leaf surfaces of Fraxinus in the southwestern USA and northwestern Mexico are sometimes white-glaucous and have been described as ‘‘papillose.’’ Individuals exhibiting this morphology have been identified as F. papillosa, a species reported from Arizona, New Mexico, Texas, and Mexico. In the original description of F. papillosa, its leaf epidermal structure was compared to F. americana L., but the abaxial surface morphology of F. papillosa is distinctly different from that of F. americana. In the latter, a cuticular reticulum overlays the epidermis and partially obscures it, while the abaxial surface of F. papillosa is similar to that of F. velutina in its lack of a cuticular overlay. In F. papillosa each epidermal cell is abruptly convex or folded upward into a papilla-like structure, compared to the relatively flat-surfaced cells of F. velutina—intergradation occurs but whether the two are appropriately considered conspecific remains to be determined. SEM photographs o...
Lundellia, 2010
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
The oak mistletoe (Phoradendron leucarpum, Viscaceae) is well-documented to exhibit preference fo... more The oak mistletoe (Phoradendron leucarpum, Viscaceae) is well-documented to exhibit preference for a few potential host species in a given locality, even when many potential host species are present. In trying to explain this distribution, we examined the mechanisms by which mistletoe seedlings recognize potentially suitable hosts in the Piney Woods ecoregion of east Texas. An initial survey of patterns of infection on the campus of Sam Houston State University revealed that water oak (Quercus nigra) was host to nearly half of the mistletoes observed, despite comprising less than 15% of trees surveyed. Field experiments demonstrated that light, host physiochemistry, and volatiles released from potential host trees serve as cues affecting the viability and establishment of mistletoe seedlings. These results provoked further study in controlled laboratory settings, in which it was demonstrated that chemical compounds in the bark of local host trees (compared to trees that serve as hosts elsewhere, but not in our survey) induce significantly although slightly greater seedling viability. Establishment of haustoria depended only on the presence of these chemicals, regardless of host species. Importantly, we demonstrated that three common monoterpenes, limonene, β-myrcene, and β-phellandrene induce a positive growth response of mistletoe radicles. These results taken together suggest a model to explain local host preference in P. leucarpum, in which covariation between mistletoe fruit maturity and monoterpene production by hosts determines the distribution of successful haustorial establishment
Recent studies of Mexican Apocynaceae have uncovered a new species. The taxon is here viewed as g... more Recent studies of Mexican Apocynaceae have uncovered a new species. The taxon is here viewed as generically distinct and accordingly the name Thoreauea paneroi J. K. Williams, gen. et sp. nov. is proposed. The species is from montane pine-oak cloud forests of the Santiago Juxtlahuaca area of northwestern Oaxaca, Mexico. Its relationship to Thenardia H.B.K. and other genera is discussed.
Heliotropium procumbens is a widespread weedy species of North America, South America and elsewhe... more Heliotropium procumbens is a widespread weedy species of North America, South America and elsewhere. It occurs in the Gulf Coastal Region (Texas, Mississippi and Louisiana) of the USA and the question is posed: is it a native or an adventive in that area? After comparing the time and location of the various Texas specimens assembled over the past 150 years or so, it is concluded that the species is native to the area concerned. Phytologia 92(2): 151-155 (August 2, 2010).
Journal of the Botanical Research Institute of Texas, 2018
The leaves of Boerhavia exhibit anisophylly. It is here hypothesized that the scale of the uneven... more The leaves of Boerhavia exhibit anisophylly. It is here hypothesized that the scale of the uneven leaves exhibits a determined pattern, rather than an arbitrary difference in size. To test for this, the opposite petioles of Boerhavia diffusa and B. erecta from both regional and local populations were measured, and the ratio of the measurements were compared to the Golden Ratio. One-paired t-tests for a critical mean indicate that the ratios of paired petioles for both species are not statically different from the value 1.6180339887…. These tests indicate that petiole length in Boerhavia approximates the Golden Ratio. The significance of this observation is that the Golden Ratio is here expressed as a line segment rather than as a spiral, which is how the Golden Ratio has been previously observed and reported in plant growth.
Lundellia, 2004
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Lundellia, 1998
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Lundellia, 2002
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Castanea, 2018
The oak mistletoe (Phoradendron leucarpum, Viscaceae) is well-documented to exhibit preference fo... more The oak mistletoe (Phoradendron leucarpum, Viscaceae) is well-documented to exhibit preference for a few potential host species in a given locality, even when many potential host species are present. In trying to explain this distribution, we examined the mechanisms by which mistletoe seedlings recognize potentially suitable hosts in the Piney Woods ecoregion of east Texas. An initial survey of patterns of infection on the campus of Sam Houston State University revealed that water oak (Quercus nigra) was host to nearly half of the mistletoes observed, despite comprising less than 15% of trees surveyed. Field experiments demonstrated that light, host physiochemistry, and volatiles released from potential host trees serve as cues affecting the viability and establishment of mistletoe seedlings. These results provoked further study in controlled laboratory settings, in which it was demonstrated that chemical compounds in the bark of local host trees (compared to trees that serve as hosts elsewhere, but not in our survey) induce significantly although slightly greater seedling viability. Establishment of haustoria depended only on the presence of these chemicals, regardless of host species. Importantly, we demonstrated that three common monoterpenes, limonene, b-myrcene, and b-phellandrene induce a positive growth response of mistletoe radicles. These results taken together suggest a model to explain local host preference in P. leucarpum, in which covariation between mistletoe fruit maturity and monoterpene production by hosts determines the distribution of successful haustorial establishment.
Phytologia., 2004
Echites exilicaulis Sesse & Moc;:. is shown to belong in the genus Mandevilla and that it is a sp... more Echites exilicaulis Sesse & Moc;:. is shown to belong in the genus Mandevilla and that it is a species distinct from Mandevilla andrieuxii (Milli. Arg.) Hemsl. Accordingly Mandevilla exilicaulis (Sesse & Moc;:.) J. K. Williams is proposed.
Journal of the Botanical Research Institute of Texas
The mitotic chromosome count (2n = 20) for Thevetia ahouai is the first reported chromosome count... more The mitotic chromosome count (2n = 20) for Thevetia ahouai is the first reported chromosome count for Thevetia sect. Ahouai. The count together with a previous count in Thevetia sect. Thevetia (also 2n = 20) provides an additional synapomorphy that further supports the monophyly of Thevetia as traditionally recognized. A discussion on the proposal to recognize Thevetia sect. Thevetia as the genus Cascabela is provided.
Lankesteriana, 2015
La nueva combinación Allotoonia woodsoniana (Monac.) J.F. Morales & J.K. Williams reemplaza al n... more La nueva combinación Allotoonia woodsoniana (Monac.) J.F. Morales & J.K. Williams reemplaza al nombre ilegítimo A. parviflora (Sessé & Moc.) J.F. Morales & J.K. Williams.
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Papers by Justin Williams