Range-wide status assessment of Houghton’s goldenrod (Oligoneuron houghtonii) with a special emphasis on niche limits, demographic transitions, and population stability

Justine Weber

SUNY College of Environmental Science and Forestry

Final Report to the Edna Bailey Sussman Foundation, 2015

Introduction

Humans are changing Earth’s landscape, and thus exerting substantial impacts on biodiversity and the function of ecological communities (Barnosky et al. 2011). Rare species, especially, may have more difficulty adjusting to climate change if narrow environmental limits are driving their rarity (Bartholomeus et al. 2011; Broennimann et al. 2006; Schwartz 2006). Additionally, species with small, specific ranges and high population densities are more vulnerable to extinction (Pimm and Raven 2000). Although rare organisms often get considerable attention in conservation, the ecology and distribution of less charismatic rare species are not well understood.

Houghton’s goldenrod (Oligoneuron houghtonii) is perennial plant of hybrid origin (Laureto and Barkman 2011) that has a geographically restricted range with approximately 80 populations found in Michigan and Ontario, and one population in New York (USFWS 1997). O. houghtonii is federally- and Michigan state-listed as threatened, is endangered in New York State, and is a species of concern in Canada (USDA 2014, COSEWIC 2005). Although it is a species of conservation concern and has a limited range, Houghton’s goldenrod is locally abundant in some interdunal wetlands, rocky shorelines, wet limestone pavements, and marl fens (USFWS 1997).

a

b

Figure 1. Houghton’s goldenrod occurrences in its core range (a) and the disjunct population in New York (b). Images from USFWS 5-year Review, 2011.

Due to its narrow range, it faces extinction or extirpation of unprotected populations. Habitat loss and fragmentation in the main Michigan coast populations are the most pressing threats (USFWS 1997), but general succession and invasive species also appear to play a role in outcompeting what appears to be an early successional plant (COSEWIC 2005; personal observation). Additionally, many populations of O. houghtonii occur in highly dynamic habitats; without a persistent seedbank, extirpation of adjacent populations could result in major losses across the species (USFWS 1997).

The Federal Recovery Plan for O. houghtonii recommended protecting 30 of the most viable elemental occurrence records (EORs, loosely populations) and their habitats as the sole delisting criteria (USFWS 1997). Currently, 42 EORs are located partially or fully on State, Federal, or land conservancy properties (USFWS 2011). While threats to this species still exist, the current status of HOGO suggests that delisting due to recovery may be appropriate. However, limited and often outdated information available for HOGO has prevented this evaluation (USFWS 2011).

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Figure 2. Houghton’s goldenrod flowering stems (a) and a marl “room” at Bergen Swamp, NY, in which the only population of NY O. houghtonii is found (b).

Completed Work

Continued monitoring of the Bergen Swamp population of Houghton’s goldenrod occurred during summer 2015. A survey of O. houghtonii flowering stems in NY revealed far fewer (~ 10%) flowering individuals than the past two years (Table 1). This was likely due to an unusually cold winter; other marl plants at Bergen Swamp (e.g. small white lady’s slipper, Cypripedium candidum and pitcher plant, Sarracenia purpurea) also had very low flower counts for the year.

Table 1. Number of O. houghtonii flowering stems at Bergen Swamp, NY.

Year

Number of flowering stems

2013

3400

2014

3000

2015

375

Additionally, in early summer 2015, a cooperative project between SUNY-ESF, the U.S. Fish and Wildlife Service (USFWS), and Michigan Natural Features Inventory (MNFI) was started to assess the status of O. houghtonii across its U.S. range. This new project will be completed and funded through the Great Lakes Restoration Initiative (GLRI), and shifted the timeline of the originally proposed Houghton’s goldenrod research. My initial objectives for the Sussman internship were to 1) investigate habitat characteristics of multiple populations to determine the drivers of species abundance and to 2) investigate the conditions necessary for Houghton’s goldenrod seed germination and establishment. These objectives will now be completed in 2016, though groundwork to fulfill these objectives was laid during summer 2015.

In order to achieve such a broad status assessment, comprehensive surveys of population numbers were initiated in summer 2015. Around 50 populations of Houghton’s goldenrod were visited in August; at each location, number of flowering stems (often rounded, as per past MNFI surveys), percent of individuals flowering, and likely threats to the population were recorded. Example data is provided in Table 2. This data will help MNFI update Houghton’s goldenrod’s state ranking, and the surveys provided valuable field observations that will guide further work. In October 2015, seeds were collected from 28 O. houghtonii populations. These seeds will be used for in situ and ex situ germination trials and viability tests.

Table 2. Example data from Houghton’s goldenrod population surveys, August 2015.

Population

Flowering Stems

Percent Flowering

Probable Threats

Summerby Fen

100

30

deer herbivory, succession

Grass Bay Preserve

>5000

20

fluctuating lake levels

Belonga Road Fen

300

20

deer herbivory, road runoff, cattail competition

Fox Point

10,000

30

fluctuating lake levels, recreational beach use, Phragmites

Cheboygan SP Beach

>3000

<10

fluctuating lake levels, recreational beach use

a

b

Figure 3. Interdunal wetland at Wilderness State Park, MI (a) and recreational beach use impacting shoreline habitat (b).

Additional field observations:

· Houghton’s goldenrod in northern Michigan was most often found in interdunal swales along Lake Michigan and Lake Huron shorelines. Moreover, it typically occurred on the upslope of the first backdune.

· Though water levels in the Great Lakes are controlled throughout the lake system, there is some fluctuation of lake levels from year to year. In August 2015, water levels in Lake Michigan and Lake Huron were close to 8 inches higher than average – a significant change when applied horizontally along shorelines. This would certainly have implications for species that depend on the narrow interdunal habitats between the lake and conifer forests nearby.

· Several Michigan sites had O. houghtonii in most disturbed locations – such as around trails or roadsides.

Future Work

Seed viability tests and greenhouse germination experiments will begin during winter 2016 and in situ germination experiments in Michigan and NY Houghton’s goldenrod populations will begin in summer 2016. Habitat data will be collected in Michigan and New York during summer 2016. These data – germination success and habitat data – will be combined using mixed models to assess what habitat variables are most associated with flowering and germination success. These results will be provided to USFWS and MNFI to update the federal and state listing status of Houghton’s goldenrod, and to assess whether it is appropriate to delist O. houghtonii from federal protection. Population surveys will also continue in summer 2016, in conjunction with MNFI botanists. Further genetic work on the species – dealing with population stability across the range – is being considered as well.

Acknowledgements

My major professor, Don Leopold, has contributed much support and advice to my continuing work. John Wiley, USFWS, aided in developing the larger range-wide project with Houghton’s goldenrod relative to federal recovery goals. Baylee Earl, my undergraduate assistant during 2015, contributed many hours and thoughtful insights in the field. And the Bergen Swamp Preservation Society, especially Steve Locke, has provided significant support and encouragement, as well as supervising this internship and providing access to Bergen Swamp and the NY Houghton’s goldenrod population. The Edna Bailey Sussman Foundation provided funding that allowed for expansion of a significant and applied conservation project, and will be recognized in my dissertation as well as in all posters, publications, and presentations wherein this work is referenced.

Literature Cited

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USDA, NRCS. 2014. The PLANTS Database. National Plant Data Team. http://plants.usda.gov. Accessed 5 March 2014.

USFWS, 1997. Recovery plan for Houghton’s goldenrod (Solidago houghtonii A. Gray). Ft. Snelling, Minnesota.

USFWS, 2011. Houghton’s Goldenrod (Solidago houghtonii A. Gray, Asteraceae): 5-Year Review. East Lansing, Michigan