Timothy J Gallaher

Timothy J Gallaher
Bernice Pauahi Bishop Museum · Natural Sciences

PhD

About

52
Publications
36,346
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855
Citations
Introduction
For the next few years - I will be 90% focused on Plants of Hawaii a new eflora and species information system. It is still in development but it will eventually live at www.plantsofhawaii.org. Still working a bit on phytoliths, Pandanaceae, Vernonieae, Grass Biogeography/morphology/anatomy/phylogeny and IndoPacific Coastal biogeography - in my free time.
Additional affiliations
March 2019 - present
Bernice Pauahi Bishop Museum
Position
  • Botanist
October 2016 - present
University of Washington
Position
  • Research Associate
January 2014 - September 2016
Iowa State University
Position
  • Research Associate
Education
September 2005 - December 2013

Publications

Publications (52)
Article
Full-text available
Grasses are widespread on every continent and are found in all terrestrial biomes. The dominance and spread of grasses and grassland ecosystems have led to significant changes in Earth’s climate, geochemistry, and biodiversity. The abundance of DNA sequence data, particularly chloroplast sequences, and advances in placing grass fossils within the f...
Article
Full-text available
Herbarium sheets present a unique view of the world's botanical history, evolution, and biodiversity. This makes them an all–important data source for botanical research. With the increased digitization of herbaria worldwide and advances in the domain of fine–grained visual classification which can facilitate automatic identification of herbarium s...
Preprint
The plant genus Bidens (Asteraceae or Compositae; Coreopsidae) is a species-rich and circumglobally distributed taxon. The 19 hexaploid species endemic to the Hawaiian Islands are considered an iconic example of adaptive radiation, of which many are imperiled and of high conservation concern. Until now, no genomic resources were available for this...
Article
Full-text available
The plant genus Bidens (Asteraceae or Compositae; Coreopsidae) is a species-rich and circumglobally distributed taxon. The 19 hexaploid species endemic to the Hawaiian Islands are considered an iconic example of adaptive radiation, of which many are imperiled and of high conservation concern. Until now, no genomic resources were available for this...
Article
Pandanus grayorum Callm., Buerki & Gallaher (Pandanaceae) is newly described from the Wet Tropics of north-eastern Queensland in Australia. It is the second Australian species other than P. gemmifer H.St.John known to reproduce by axillary plantlets on aerial branches. It can be distinguished from P. gemmifer and P. solms-laubachii F.Muell. by the...
Article
Full-text available
Premise: With over 1500 species, the globally distributed Vernonieae is one of the most successful members of the Compositae. However, due to its morphological complexity and limited geographic representation in previous studies, subtribal and biogeographic relationships are unclear. Here new DNA sequence data spanning the geographical range of the...
Article
Full-text available
This article comments on: Kristýna Hošková, Adéla Pokorná, Jiří Neustupa and Petr Pokorný, Inter- and intraspecific variation in grass phytolith shape and size: a geometric morphometrics perspective, Annals of Botany, Volume 127, Issue 2, 01 February 2021, Pages 191–201, https://doi.org/10.1093/aob/mcaa102
Article
Pandanus odorifer (Pandanaceae) is an economically important species distributed on coasts from India and Sri Lanka to South China through tropical Asian countries. Pandanus odoratissimus has been widely used as the accepted name for the species, but P. odoratissimus is in reality a superfluous and illegitimate name. No original material of P. odor...
Article
Full-text available
Process‐based vegetation models attempt to represent the wide range of trait variation in biomes by grouping ecologically similar species into plant functional types (PFTs). This approach has been successful in representing many aspects of plant physiology and biophysics but struggles to capture biogeographic history and ecological dynamics that de...
Conference Paper
Modern grasses in the family Poaceae exhibit exceptional taxonomic and ecological diversity, with grassland-dominated habitats covering about 40% of Earth’s land surface. Grasslands today occur in a range of temperate to tropical ecosystems, spanning low to high altitudes and wet to arid climates. However, because of the scant fossil record of gras...
Article
We used a bi‐organellar phylogenomic approach to address higher‐order relationships in Pandanales, including the first molecular phylogenetic study of the panama‐hat family, Cyclanthaceae. Our genus‐level study of plastid and mitochondrial gene sets includes a comprehensive sampling of photosynthetic lineages across the order, and provides a framew...
Article
Rationale: Fossil grass silica short cell phytoliths (GSSCP) have been used to reconstruct the biogeography of Poaceae, untangle crop domestication history, and detect past vegetation shifts. These inferences depend on accurately identifying the clade to which the fossils belong. Patterns of GSSCP shape and size variation across the family have not...
Preprint
Rationale: Fossil grass silica short cell phytoliths (GSSCP) have been used to reconstruct the biogeography of Poaceae, untangle crop domestication history, and detect past vegetation shifts. These inferences depend on accurately identifying the clade to which the fossils belong. Patterns of GSSCP shape and size variation across the family have not...
Preprint
With over 1500 species, the Vernonieae is one of the most successful members of the largest family of flowering plants, the Compositae. However, due to morphological complexity and limited geographic representation in previous studies, relationships within the tribe have been difficult to understand. We bring new DNA sequence data spanning the geog...
Article
Full-text available
Hawaiian plant radiations often result in lineages with exceptionally high species richness and extreme morphological and ecological differentiation. However, they typically display low levels of genetic variation, hindering the use of classic DNA markers to resolve their evolutionary histories. Here we utilize a phylogenomic approach to generate t...
Preprint
Full-text available
Process-based vegetation models attempt to represent the wide range of trait variation in biomes by grouping ecologically similar species into plant functional types (PFTs). This approach has been successful in representing many aspects of plant physiology and biophysics, but struggles to capture biogeographic history and ecological dynamics that d...
Article
Full-text available
Grass leaf shape is a strong indicator of their habitat with linear leaves predominating in open areas and ovate leaves distinguishing forest‐associated grasses. This pattern among extant species suggests that ancestral shifts between forest and open habitats may have coincided with changes in leaf shape or size. We tested relationships between hab...
Data
VIDEO S1. An animation of the steps required for 3D modeling of spikelets using Cinema 4D software. This video is an MP4 file and is available under the Supporting Information section at the end of the article, or can be viewed from the https://youtu.be/BAqwqSD0e9E.
Article
Full-text available
Premise of the Study A refined procedure is described for modeling small, intricate plant structures using computer‐aided design software. The procedure facilitates the study of wind pollination in the family Poaceae and provides virtual biological illustrations for public outreach. Methods and Results Spikelets were fixed in gFAA, dehydrated usin...
Article
Full-text available
Current morphometric methods that comprehensively measure shape cannot compare the disparate leaf shapes found in seed plants and are sensitive to processing artifacts. We explore the use of persistent homology, a topological method applied as a filtration across simplicial complexes (or more simply, a method to measure topological features of spac...
Preprint
Full-text available
Current morphometric methods that comprehensively measure shape cannot compare the disparate leaf shapes found in seed plants and are sensitive to processing artifacts. We explore the use of persistent homology, a topological method applied across the scales of a function, to overcome these limitations. The described method isolates subsets of shap...
Presentation
Pandanus tectorius Parkinson (senso lato), is a widespread small tree found in the tropics, in coastal strand habitats and sometimes inland on low elevation slopes of moderately wet to wet valleys up to about 600 meters. Its native range extends from Australia through parts of mainland and insular Southeast Asia into both Near and Remote Oceania. T...
Article
Full-text available
Species of the temperate woody bamboo genus Kuruna Attigala, Kathriar. & L.G. Clark (Poaceae: Bambusoideae) distributed in Sri Lanka and southern India, are threatened due to deforestation and habitat fragmentation. The current study focused on the tetraploid woody bamboo Kuruna debilis (Thwaites) Attigala, Kathriar. & L.G. Clark, using twelve vari...
Article
Full-text available
Aim To test for and describe genetic structure within the Pandanus tectorius complex, a group of closely related ocean-dispersed plants and members of the Indo-Pacific coastal strand community. Location Tropical Indo-Pacific (coastal East Africa to Polynesia). Methods We sampled 535 individuals (46 localities) from throughout the range. Fifteen mic...
Conference Paper
Full-text available
Grasses have adapted to a remarkable breadth of habitats. They are best known from open grasslands and croplands which today cover over 40% of the Earth’s terrestrial surface; however, the family also has members, including the oldest extant lineages, which are found in deeply shaded forest understories or more open woodlands. Some grasses have ada...
Article
Full-text available
This study investigates the biogeography, evolution and systematics of Benstonea Callm. & Buerki (Pandanaceae) based on six plastid DNA regions and 54 specimens representing 36 species (60 % of species generic diversity). Our maximum likelihood and Bayesian phylogenetic inferences support the monophyly of Benstonea and its close relationship with t...
Conference Paper
Root systems extract water and essential nutrients from the soil, supplying the plant’s vegetative and reproductive structures. Despite this importance, the role of roots has been historically downplayed by comparison to their aboveground counterparts. Furthermore, morphological and anatomical features that occur within a root’s architecture, espec...
Conference Paper
Full-text available
Nearly all of the energy used by living beings is captured first through the process of photosynthesis. Most terrestrial photosynthesis takes place in the specialized chlorenchyma cells of plant leaves. These cells show substantial variation in size and shape among species resulting in different arrangements of chloroplasts, surface area to volume...
Article
Full-text available
Pandanaceae (screwpines) is a monocot family composed of c. 750 species widely distributed in the Paleotropics. It has been proposed that the family may have a Gondwanan origin with an extant Paleotropical distribution resulting from the breakup of that supercontinent. However, fossils supporting that hypothesis have been recently reassigned to oth...
Chapter
In Hawaiʻi, hala or pūhala refers to species of small, often coastal, trees in the genus Pandanus. Hala is among the most important plants in the ecology and history of Hawaiʻi and the broader Pacific. Once a major native component of the coastal and lowland areas of Hawaii, hala forests have been nearly eliminated by human activity, and with them...
Article
Full-text available
The Paleotropical monocot family Pandanaceae includes ca. 700 species assigned to four genera: Pandanus (ca. 500 spp.), Freycinetia (ca. 200 spp.), Martellidendron (6 spp.) and Sararanga (2 spp.). The most speciose genus, Pandanus, was classically subdivided into eight subgenera. Previous cladistic analyses revealed that several key morphological c...
Article
Full-text available
We coordinated biogeographical comparisons of the impacts of an exotic invasive tree in its native and non-native ranges with a congeneric comparison in the non-native range. Prosopis juliflora is taxonomically complicated and with P. pallida forms the P. juliflora complex. Thus we sampled P. juliflora in its native Venezuela, and also located two...
Data
Summary of statistical analysis of pH, electrical conductivity (EC), organic carbon (OC), phosphate-P and total organic N (TON) of soil treated with no leachate (control, C), P. cineraria (PC) or P. juliflora (PJ) leaf leachate (one-way ANOVA and posthoc Tukey’s test at p<0.05). (DOCX)
Data
Summary of statistical analysis of total phenolic content of soil treated with no litter (control, C), P. cineraria (PC) or P. juliflora (PJ) leaf litter at rate of 12 mg/g soil, and incubated for 0, 1, 2, 3, 4, 6, 8, 10 and 14 days. (DOCX)
Article
Full-text available
Prosopis pallida and P. juliflora (commonly referred to as algarroba, mesquite, or kiawe) were introduced from South America to areas in Oceania, Asia, and Africa during the early nineteenth century. In many cases, they naturalized and became widespread. In some places, alien Prosopis species are highly valued for the products and services that the...
Article
Full-text available
Prosopis pallida and P. juliflora (commonly referred to as algarroba, mesquite, orkiawe) were introduced from South America to areas in Oceania, Asia, and Africa during the early nineteenth century. In many cases, they naturalized and became widespread. In some places, alien Prosopis species are highly valued for the products and services that they...
Article
Full-text available
Measuring the “importance” of plants and vegetation to people is a central concern in quantitative ethnobotany. A common tool to quantify otherwise qualitative data in the biological and social sciences is an index. Relative cultural importance (RCI) indices such as the “use values” developed by Prance et al. (1987) and Phillips and Gentry (1993a,...
Article
Full-text available
Measuring the " importance " of plants and vegetation to people is a central concern in quantitative ethnobotany. A common tool to quantify otherwise qualitative data in the biological and social sciences is an index. Relative cultural importance (RCI) indices such as the " use values " developed by Prance et al. (1987) and Phillips and Gentry (199...

Questions

Question (1)
Question
I am using the first principal component of morphometric data as a response variable in a PGLS analysis. Log transformation of this variable produces residuals which have a better fit. Are there any issues with transforming principal component scores? 

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Projects

Projects (5)
Project
We are building an information portal that will cover all of the native and naturalized plants in Hawaii. Plants of Hawaii will feature up to date taxonomy, new descriptions. keys, images, and search functions to identify plants... and a geographic species information system.
Project
Using the Bamboo subfamily as a test case, we developed confocal microscopy and image processing techniques to create 3D surface representations of short cell phytoliths. We used geometric morphometric techniques to quantify surface shape and applied machine learning algorithms as a tool to identify the affinity of phytoliths at various taxonomic levels. Using these techniques we achieved a high degree of correct automatic classification of the phytoliths at sub-familial, tribal and genus level ranks. The 3D objects produced during this study will contribute to a family wide digital reference collection for use by paleobotanists and grass taxonomists worldwide.