Common hoptree (Ptelea trifoliata) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

Population numbers appear to be in a slight decline of about 12%, with the extirpation of three of the 26 populations known in 1982-4; these have been lost due to human activity near their shoreline habitat. Four new sites (plus population extensions) were recorded since 1984, but they may have been overlooked earlier rather than being new (recently established) populations; most are near known populations. Six populations have shown declines (# 3, 10, 11, 14, 24 and 28), 11 are stable or showing increases over 1982 (#2, 6, 8, 9, 15, 17, 20, 21, 22, 23, and 25); Point Pelee appears to be in a decline similar to Fish Point, but there were no previous counts to compare with the present situation.

A larger decline in numbers of reproductive individuals, about 43%, was observed among those 17 populations with comparative data. Careful documentation of the Fish Point site shows a large decline of 60% in 17 years. However, this apparent trend seems less significant when the much larger populations without comparative data are included. The decline of several small populations and the loss of three is a concern and action should be taken to reduce the activity that causes their decline, but overall the decline of the Ontario population is likely somewhere between the above 43% and the estimated numbers at the end of the table below that suggest a low decline. It is estimated that there are an additional 300-450 trees not accounted for in Table 1 at Point Pelee and other sites not resurveyed in 2000-02 for a total of about 920-1025 reproductive trees. Three populations on protected sites have 100 to 300+ individuals each.

The surveyed sites are summarized in table 1.

Table 1. Subset of Ontario Populations of Ptelea trifoliata
(primarily of sites with comparative data)
Number County or Region Population Ambrose & Aboud, 1982 2000-02 survey
2 Elgin County Port Burwell Provincial Park 2 + 0 + 10Footnotea 12 + 40 + 40; TH: IE
3 Essex County Colchester, public beach 1 + 0 + 0 0 + (1) + 0; TH: BG
6 Essex County Fox Creek Conservation Area 0 + 2 + sev 1 + 0 + 1 TH: ID
8 Essex County Cedar Beach Conservation Area 0 + 3 + 0 2 + 3 + 18 TH: BG
9 Essex County West of Comet 2 + 0 + sev 7 + 1 + 0
10 Essex County Holiday Beach Conservation Area 4 + ~ 15 + 15 2 + 2 + 0 TH: BG
11 Essex County Hillman Marsh sand spit  ~20 1 + 0 + 0 TH: SE, TBB
12 Essex County PointPelee National Park Numerous Numerous
14 Essex County Fish Point + 248+num+num 96 + 13 + 8 TH: TBB, IE
15 Essex County Stone Road Alvar, roadside 5 + few + sev 10 + 4 + 0
17 Essex County West Shore roadside Common 50 + 57 + 0
20 Essex County Lighthouse Point and quarry roadside 11 + ? + sev 55 + 20 + 0
21 Essex County Middle Island num + num + ? 300 + 22 + 0; TH: CN
22 Kent County Rondeau Provincial Park 6 + 1 + sev 4 + 32 + 28 TH: DB
23 Kent County Erieau Beach 6 + 4 + num 7 + 6 + num. TH: BG
24 Kent County Thamesville, Glacial shoreline 22 + few + sev 6 + 5 + 0 TH: ID
25 Lambton County Walpole Island 1 + 0 + 0 2 + 0 + 0
28-32 Niagara Region Crescent Beach to Windmill Point 37 +14 + 0-num 16 + 9 + 0-few; TH: BG
7 Essex County Linden Beach 1 + 0 + sev. Extirpated TH: BG
13 Essex County Seacliff [1987: no abundance data] Extirpated TH: BG
27 Niagara Region Erie Beach ~25 + ? + ? Extirpated TH: ID, BG
Total     391 + 39 + 25Footnoteb 221 + 136 + 95Footnotec

+The Fish Point population was comprehensively inventoried in 1983 and again in 2000.

TH = Threats: BG, beach grooming; DB, deer browsing; ID, incompatible development; IE, invasive exotics; SE, storm erosion; TBB, twig boring beetle; CN, cormorant nesting.

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