Nova Scotia Provincial Status Report Spotted Pondweed
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Nova Scotia Provincial Status Report on Spotted Pondweed (Potamogeton pulcher Tuckerm.) prepared for Nova Scotia Species at Risk Working Group by David Mazerolle and Sean Blaney Atlantic Canada Conservation Data Centre P.O. Box 6416, Sackville, NB E4L 1C6 DRAFT Funding provided by Nova Scotia Department of Natural Resources Submitted December 2010 EXECUTIVE SUMMARY i TABLE OF CONTENTS EXECUTIVE SUMMARY ..................................................................................................i WILDLIFE SPECIES DESCRIPTION AND SIGNIFICANCE...........................................1 Name and Classification............................................................................................1 Morphological Description ........................................................................................2 Field identification......................................................................................................3 Designatable Units .....................................................................................................4 Special Significance...................................................................................................5 DISTRIBUTION ...............................................................................................................7 Global Range ..............................................................................................................7 Canadian Range .........................................................................................................8 Search Effort.............................................................................................................15 HABITAT .......................................................................................................................17 Habitat Requirements ..............................................................................................17 Habitat Trends ..........................................................................................................18 BIOLOGY ......................................................................................................................18 Life Cycle and Reproduction...................................................................................19 Physiology and Adaptability ...................................................................................20 Dispersal and Migration...........................................................................................21 Interspecific Interactions.........................................................................................21 POPULATION SIZES AND TRENDS............................................................................22 Abundance................................................................................................................22 Fluctuations and Trends..........................................................................................24 Rescue Effect............................................................................................................25 THREATS AND LIMITING FACTORS ..........................................................................25 PROTECTION, STATUS, AND RANKS........................................................................27 Legal Protection and Status....................................................................................27 Non-Legal Status and Ranks...................................................................................27 Habitat Protection and Ownership..........................................................................28 ACKNOWLEDGEMENTS AND AUTHORITIES CONTACTED ....................................28 INFORMATION SOURCES...........................................................................................28 BIOGRAPHICAL SUMMARY OF REPORT WRITER(S) ..............................................34 COLLECTIONS EXAMINED .........................................................................................34 ii List of tables Table 1. Location, observer and survey date for all confirmed Spotted Pondweed (Potamogeton pulcher) populations, with notes on abundance and habitat. List of figures Figure 1. Spotted Pondweed (Potamogeton pulcher) with prominent floating leaves growing in its natural habitat in association with Purple bladderwort (Utricularia purpurea) and Greater bladderwort (Utricularia macrorhiza). Figure 2. Line drawing of Spotted Pondweed (Potamogeton pulcher) showing spotted stem, floating leaf shape, submersed leaf shape, inflorescence and fruit shape (source: Holmgren 1998). Figure 3. Global distribution of Spotted Pondweed (Potamogeton pulcher). Range outlined in the United States is based on state-level distribution data (Natureserve 2010). Range in Canada is identified by points corresponding to known occurrences. Figure 4. Distribution of Spotted Pondweed (Potamogeton pulcher) in Nova Scotia. Numbers refer to those used in Table 1. The twelve confirmed populations are: 1) Rhodenizer Lake, 2) Maitland Pond, 3) Hirtle Lake, 4) Charleston, 5) Mill Village, 6) Buggy Hole Brook, 7) Shingle Lake, 8) Carrigan Lake, 9) Placides Lake, 10) Raynards Lake, 11) Salmon Lake and 12) Upper Musquodoboit. Figure 5. Distribution of Spotted Pondweed (Potamogeton pulcher) in Queens County and Lunenburg County, Nova Scotia. Numbers refer to those used in Table 1. The eight confirmed populations in this region of occurrence are: 1) Rhodenizer Lake, 2) Maitland Pond, 3) Hirtle Lake, 4) Charleston, 5) Mill Village, 6) Buggy Hole Brook, 7) Shingle Lake and 8) Carrigan Lake. Figure 6. Distribution of Spotted Pondweed (Potamogeton pulcher) in Yarmouth County and Digby County, Nova Scotia. Numbers refer to those used in Table 1. The three confirmed populations in this region of occurrence are: 9) Placides Lake, 10) Raynards Lake and 11) Salmon Lake. Figure 7. Distribution of Spotted Pondweed (Potamogeton pulcher) in Halifax County, Nova Scotia. Number refers to that used in Table 1. The only confirmed population in this region of occurrence is at Upper Musquodoboit (12). Figure 8. Atlantic Canada Conservation Data Centre rare plant survey sites visited in Queens, Lunenburg and Annapolis counties from 2007 to 2010. Stars indicate survey sites where previously unknown Spotted Pondweed (P. pulcher) populations were discovered. iii WILDLIFE SPECIES DESCRIPTION AND SIGNIFICANCE Name and Classification Scientific Name: Potamogeton pulcher Original Description: Tuckerman, 1843 Synonyms: Potamogeton amplifolius var. ovalifolius Morong ex Benn., 1904 Potamogeton amplifolius f. amphibius Benn., 1904 Potamogeton amplifolius var. amphibius (Benn.) Graebn., 1907 Spirillus pulcher (Tuckerman) Nieuwl., 1913 Potamogeton pulcher f. amphibius Hagstr., 1916 English vernacular name: Spotted Pondweed, Heartleaf pondweed French vernacular name: Potamot gracieux Genus: Potamogeton L. (Pondweed) Family: Potamogetonaceae (Pondweed family) Order: Najadales Subclass: Alismatidae Class: Liliopsida (Monocotyledons) Major plant group: Magnoliophyta (Angiosperms) Spotted or Heartleaf pondweed (Potamogeton pulcher) was described by American botanist Edward Tuckerman in 1843 from specimens collected in Massachusetts. He must have been quite taken by the species, assigning it a specific epithet that translates to “beautiful” or “handsome”. During the early 20th century, taxonomic revisions of the pondweed family and difficulties in defining taxa in a group prone to hybridization and morphological variation resulted in P. pulcher being given several other names. Three of these involved the relegation of this species to a variety or form of Large-leaf Pondweed (Potamogeton amplifolius), the species which Spotted Pondweed most closely resembles. Recent treatments of Potamogeton have upheld the taxon as a distinct species (BONAP 2010, Haynes and Hellquist 2000, Natureserve 2010). The pondweed family (Potamogetonaceae) is one of the most common and widespread groups of aquatic vascular plants on the planet (Pip 1987). The pondweed genus (Potamogeton) includes approximately 100 species (Haynes and Hellquist 2000, Wiegleb 1988), 33 of which are found in North America (Haynes and Hellquist 2000). Most are of the northern hemisphere and the highest specific densities are found in eastern North America, Western Europe, Siberia and Japan (Wiegleb 1988), where numerous species may co-occur within a site (Pip 1987, see also BONAP 2010, Haynes and Hellquist 2000). Pondweeds are a major source of food and shelter for animals, and are among 1 the most important vascular plants in aquatic ecosystems (Barrat-Segretain 1996, Newman 1991, Wiegleb et al. 1991). The significant range of environmental variation displayed by pondweeds and the fact that plants often remain infertile (thus lacking fundamental diagnostic features), have made understanding of this group difficult (Ogden 1943). Species are also known to hybridize frequently and hybrids comprise an important part of pondweed diversity (Kaplan and Fehrer 2006, Ogden 1943, Wiegleb and Kaplan 1998). In addition to the ca. 100 species in the genus, Wiegleb and Kaplan (1998) recognize 50 hybrids as being well established and distinguishable from the parent species, while noting that many other hybrids proposed in the literature require further investigation. Although the genus has been divided into several sections and subsections, these have not been retained in the most recent North American taxonomic treatment (Haynes and Hellquist 2000).