I LLINOI S UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN PRODUCTION NOTE University of Illinois at Urbana-Champaign Library Large-scale Digitization Project, 2007. The Population Biology of Torreya taxifolia: Habitat Evaluation, Fire Ecology, and Genetic Variability Mark W. Schwartz and Sharon M. Hermann Center for Biodiversity Technical Report 1992(Z) Illinois Natural History Survey 607 E. Peabody Drive Champaign, Illinois 61820 Tall Timbers, Inc. Route 1, Box 678 Tallahassee, Florida 32312 Prepared for Florida Game and Freshwater Fish Commission Nongame Wildlife Section 620 S. Meridian Street Tallahassee, Florida 32399-1600 Project Completion Report NG89-030 TABLE OF CONTENTS page Chapter 1: Species background and hypotheses for.......5 the decline of Torreya taxifolia, species Background ....... .. .6 Hypotheses for the Decline........0 Changes in the Biotic Environment ...... 10 Changes in the Abiotic Environment ..... 13 Discu~ssion *0o ** eg. *.*. 0 0*.0.*09 6 0 o**** o*...21 Chapter 2: The continuing decline of Torreyap iola....2 Study.Area and Methods ooo................25 Results * ** ** ** ** ** ** .. .. .. .. .. .. .. .. .. .. .30 Chapter 3: Genetic variability in Torreya taxif-olia......4 Methods.......................* 0 C o490 0 Results . ...... *oe*.........o51 -0L-icmion *.. ~ 0000 00000@55 Management _Recommendations .000000000000.0.60 Chapter 4: The light relations of Tgr .taz'ifgli with ..... 62 special emphasis on the relationship to growth and,,disease- Methods o..............0.0.0.0.0.00.eoo63 Light and Growth . .. .. .. .. .. .. .. .. .. .. .64 Measurements'-of photosynthetic rates 0,.65 Light and Growth . .. .. .. .. .. .. .. .. .. .. .69 Measurements of photosynthetic rates ..71. Discussion......... *0* * * * * * * ** . 81 Chapter 5: The foliar fungal associates of Torreya............85 ta ifola: pathogenicity and susceptibility to smoke Methods 0 0 0... 0..0.....0..0..0..0..0..0..0..0..0. *86 Fungal Isolation 00000-0900960000000690086 Pathogenicity Tests *00000....00.0.0.087 Fungal.Susceptibility to Smoke ........ 87 Field Tests of Smoke Hypothesis ....... 90 Results............00000000000000 .000000000*91 Fungal Isolation and Pathogenicity ....91, Smoke Susceptibility ..... oo............92 Discussion..................000 00000000000098 2 FIGURES Chapter 1 page 1.1 Range Map of Torreya taxifolia ........................... 7 1.2 Annual Precipitation in Blountstown, FL, 1922-1982 ...... 14 1.3 Water Temperature Data, Above and Below Lake Seminole ...16 1.4 Air Temperature Data, Blountstown, FL, 1931-1984 ........ 18 Chapter 2 2.1 Range Map Detailing Study Areas ......................... 26 2.2 Stem Size Distribution for Census Population ............ 31. 2.3 Number of Stems per Individual .......................... 31 2.4 Distribution of T. taxifolia With Respect to Elevation ..34 2.5 Distribution With Respect to Canopy Cover ............ 34 2.6 Distribution With Respect to Aspect ..................... 34 2.7 Apparent Age Distribution of Census Population .......... 36 2.8 Age Correction Regression ............................... 36 Chapter 3 3.1 Map of Sampled Populations..............................50 BLANK PAGE ............. .. *****..* ***************. * * *.. 53 3.2 Cluster Diagram of Populations ..........................58 Chapter 4 4.1 Comparison of Growth by Light ........................... 70 4.2 Light Saturation Photosynthesis Curve ................... 73 4.3 Photosynthetic Rates of Diseased Versus Healthy Needles .74 4.4 Photosynthetic Rates by Needle Age ...................... 75 4.5 Light Saturation Curves for Five Closely Related Species.77 4.6 Photosynthetic Rates Across Relative Humidity, 5 Species.78 4.7 Photosynthetic Rates Across Temperature, 5 Species ...... 79 4.8 Rate of Water Loss in Absence of Watering, 5 Species ....80 4.9 Photosynthetic Rates Across.Water Stress, 5 Species ..... 80 Chapter 5 5.1 Smoke Residue Deposition Versus Time Treatment .......... 89 5.2 Effects of Direct Smoke Treatment on Fungal Growth ...... 93 5.3 Effects of Smoke Residue on Fungal Growth ............... 94 5.4 Effects of Smoke Residue on Spore Germination Rate ...... 95 5.5 Effects of Smoke Residue on Spore concentration ......... 96 5.6 Effects of Smoke Residue on Spore'Growth Rate ........... 97 Chapter 6 None TABLES Chapter 1 page 1.1 Fungal Associates of Torreya taxifolia .................. 9 1.2 Hypotheses for the Decline of T. taxifolia ............. ll Chapter 2 2.1 Census Population ......................................28 2.2 Mean Length of Longest Stem, by Population ............. 33 2.3 Frequency of Disease Symptoms ..........................38 2.4 Growth Fate of T. taxifolia, by Size Class ............. 38 2.5 Growth Fate of T. taxifolia, by Disease Load ........... 42 Chapter 3 3.1 Allele Frequencies for Enzymes Studied ................. 52 3.2 Heterogeneity of Sampled Populations ................... 54 3.3 Genetic Distance Between Sampled Populations ........... 56 3.4 Genetic Diversity Within and Between Populations ....... 57 Chapter 4 4.1 Growth Fate of Trees in Different Canopy Cover Classes .72 4.2 Disease Incidence of Trees in Canopy Cover Classes ..... 72 Chapter 5 5.1 Fungi Isolated From T. taxifolia Used in Experiments ...89 Chapter 6 None CHAPTER 1 Species background and hypotheses for the decline of Torreva taxifolia During the late 1950's, Torreya taxifolia suffered from a catastrophic decline, presumably fungal in origin, that decimated adult populations throughout its range (Godfrey and Kurz 1962). The cause of this decline remains a mystery; no specific pathogen has been implicated (Alfieri et al. 1967, USFWS 1986); the predominant speculation is that any of a combination of several environmental changes rendered T. taxifolia more susceptible to native pathogens (USFWS 1986). Four hypotheses for the cause of the decline of T. taxifolia have been proposed (Alfieri et al. 1967, Toops 1981, Barnes 1985, USFWS 1986). Correlative evidence to address two of these hypotheses is presented here. In addition, five new hypotheses for the decline, and evidence to assess two of these hypotheses, are presented here. Direct evidence to adequately test any of the hypotheses is mostly lacking because no healthy individuals remain in the wild, no undisturbed habitat remains, and the primary pathogen eludes discovery. With this lack of direct evidence, we are left to piece together anecdotal and correlative evidence as to the cause of the dieback. Providing management to facilitate recovery of T. taxifolia is also hindered by a lack of sufficient information. The purpose 5 of this chapter is to discuss the relative merits of different hypotheses proposed to explain the decline. The results presented here point toward management recommendations despite an inherent inability for adequate testing of virtually any hypothesis. This chapter discusses, by example, the difficulty in isolating pathogen-induced declines in endangered species, and how to approach management recommendations given this information gap. SPECIES BACKGROUND Florida torreya (T. taxifolia, Taxaceae) is an endemic conifer restricted to ravine slopes along the eastern side of the Apalachicola River in the central panhandle of Florida (Figure 1.1). This dioecious evergreen tree can grow up to 20m in height at maturity (Godfrey 1988) and was formerly a common understory tree in the region (Chapman 1885, Harper 1914, Reinsmith 1934, Kurz 1838a, 1938b). The ravine habitats which support T. taxifolia are characterized by a diverse mixture of hardwoods and conifers, most notably beech (Fagus grandifolia), and magnolia (Magnolia grandiflora), along with various oaks and hickories along upper slopes (Platt and Schwartz 1990, Schwartz 1990). Several factors reduced the abundance of the species prior to the decline. In the 1800s, T.. taxifolia was cut along the Apalachicola River for fuel (Chapman 1885, Gray 1889), and for fenceposts and shingles through the 1900s (Chapman 1885, Reinsmith 1934, Kurz 1938b, Burke 1978). However, T. axifolia only became endangered after a catastrophic decline during the 1950s. This decline is thought to have been caused by fungal Figure 2.2.. The range of Torreya taxifolia, including an outlying population in the vicinity of Lake Ocheese-e. Habitat features digitized from 1953 and 1955 USDA aerial photographs using ARC/INFO ver 5.0. Tgrreya~tYa x±i.I is restricted within its range to floodplain and ravine habitats. Rangeof Torreya taxifolia Suitable Habitat Other Land Cover r -r 1 10 KM *Floodplain *Towns flRavines SAgriculture ElForested Uplands ILa Uswekemined From USOA kqIW PhonogrrKgy, 1953-105 pathogens, although no primary pathogen has been identified (Godfrey & Kurz 1962, Alfieri et al. 1967, 1984). The apparent lack of an introduced pest is unusual among catastrophic diebacks of fungal origin (Manion 1981). By 1962, virtually no adult T. taxifolia remained in the wild (Godfrey and Kurz 1962). Recent censuses indicate that approximately 1000 juveniles, and no adults, remain in the wild (Baker 1982, Chapter 2). Most individuals in the wild are less than 2 m tall, are sexually immature, and carry symptoms of foliar diseases (Chapter 2). Few specifics were recorded about the decline of the Tv taxifolia. The earliest observation of disease symptoms may have been in 1938 (Nieland, pers. comm. as cited in Alfieri al. 1967), however, other reports from this decade make no mention of disease (Reinsmith 1934, Kurz 1938a, 1938b). The next report of disease came from Torreya State Park in 1955 (USFWS