Table 1. Summary of Cirsium hillii occurrences by state and province, with a breakdown by last observation date. (#=footnotes)
State or Element Rank Number of Last Last Observed Last Last Observed Unknown Province (#3) Occurrences Observed 1950-1971 Observed pre-1900 Observation Recorded 1972-1997 1900-1949 Date Illinois S1 39 38 1 Indiana S1 16 5 0 9 2 Iowa S1 5 5 * * * Michigan S3 130 102 14 9 5 Minnesota S3 58 37 2 9 8 2 Ohio SRF (#4) 0 - - - - - Wisconsin S2 68 34 11 19 3 1 Ontario S2 ~40 (#5) - - - - Totals: - 356 221 28 46 16 5
* Historical occurrences documented through several collection records include this category but were not provided in the state status report and thus cannot be detailed here. The number of occurrences recorded for Iowa only reference confirmed extant populations .
3 The sub-global rank for Hill's thistle within the states and province in its range.
4 Reported falsely within the state.
5 Because the number of Ontario sites are estimated from numerous collection records, a breakdown by collection period cannot be provided.
1) Heritage programs track must track species (i.e. "elements") on an arbitrarily determined locality basis for their databases. Thus, an occurrence may not necessarily constitute what one might consider a population, and in many cases may represent a series of colonies or patches that can be collectively be described as metapopulations.
2) Appendix A provides an explanation of Nature Conservancy element occurrence ranks.