Plants of Southern California: Distinguishing Collinsia concolor and C. heterophylla
Table of Contents
IntroductionDistinguishing Characteristics
Geographic Distribution of These Taxa in the Cuyamaca Mountains
C. concolor | C. heterophylla |
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| Fig. 1. Frontal view of a flower of Collinsia concolor (left) and C. heterophylla (right).
Top row. Left: Unlabeled pix from an iNat observation of C. concolor by Jason Schock. Right: Unabeled pix from an iNat observation of C. heterophylla by Don Rideout. Bottom row. Pix labeled with some of the differences between these two species. | |
C. concolor | C. heterophylla |
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| Fig. 2. Side view of a flower of Collinsia concolor (left) and C. heterophylla (right).
Top row. Left: Unlabeled pix from an iNat observation of C. concolor by Jason Schock. Right: Unabeled pix from an iNat observation of C. heterophylla by Don Rideout. Bottom row. Pix labeled with some of the differences between these two species. | |
I checked how well the discriminants shown in Figs. 1 and 2 worked by looking at random samples of both species in San Diego County using iNat observations.
For C. heterophylla, I drew a geographic line as shown in Fig. 3, which separates an area with only C. heterophylla in San Diego County, from vouchers, from an area that has both species present.
Fig. 3. Geographic distribution of Collinsia concolor and C. heterophylla from the San Diego County Plant Atlas page, retrieved on 27 May 2024, with a line drawn to separate the area to the west containing only C. heterophylla from the area to the east where both species are present. See Fig. 6 below for the plot produced by the Plant Atlas with the topography of San Diego County shown.
I examined 26 random observations determined at iNat as C. heterophylla. I used a random number generator to order all the iNat obs of C. heterophylla in the area I selected, and then went through the list in the order of the random number.
One of those 26 observations was actually Linaria maroccana; another was a young plant with no flowers. 17 of the remaining 24 observations I verified as C. heterophylla, since they had square blotch areas. 15 of those 17 also had a clear red line present, and a dark red corolla throat. Two of those 17 also had one of those two traits visible. The other 7 of those observations did not have good enough pix to see the blotch, red line, or throat color clearly, but from what I could see of those flowers fit C. heterophylla.
I examined 31 random iNat observations determinated as C. concolor. Two of those observations turned out to actually be C. heterophylla, with square blotch areas, a red line present, and a dark red throat color. I added that determination to their iNat observations, and did nothing further with those observations. Eight of the 31 had pix that were not good enough to check the differentiating characteristics shown in Figs. 1 and 2, so I ignored those. Of the remaining 21 observations, 20 clearly had a triangular blotch area. The other one of those 21 observations had a corolla throat longer than wide. So all 21 were C. concolor.
The lower lip color showed less variation than the upper lip color in both of these species. Most iNat observations of both species had a pink-purple lower lip, ranging from light to dark pink-purple. Some lower lips of C. heterophylla were blue-purple, as was one flower of C. concolor.
The upper lip was white for 17 of the C. heterophylla observations, sometimes tinged pink-purple. Another four were pink-purple, and one was bluish white.
The upper lip had at least some blue color for 13 of the C. concolor observations, often present on just the tips of the upper lobes. Another seven were whitish and tinged with pink-purple or blue. Another one was a light pink-purple.
Some of the variation in the flowers of C. concolor in those observations I checked are shown in Fig. 4, and for C. heterophylla in Fig. 5.
It was difficult to find a good way to order the photographs of each species. In the end, I decided to order the photographs of C. concolor by the amount of blue color in the upper lip, since that was considered important by the authors of the Flora of North America treatment. This is a subtle distinction for many of the flowers, and undoubtedly different people would order the photographs differently.
The photos of C. heterophylla are organized by the color of the lower lobes, since even though most had a pink-purple lower lip, there was still a good variation in the intensity of the color.
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| Fig. 4. Variation in the flowers of C. concolor. The photographs are arranged in order of the color of the upper lobes, by the amount of bluish color, since that was considered important by the authors of the Flora of North America treatment. This is a subtle distinction for many of the flowers, and undoubtedly different people would order the photographs differently.
The photos come from all iNat observations that I examined which had a good frontal view of the flowers, were in focus, and had flowers that were comparable in size to the others in this Figure. All of the flowers have a triangular blotch area, although that is less apparent when the upper lobes are more spread apart. None of the flowers have the dark throat of C. heterophylla, and only a few have what might be considered a red line formed by the blotches near the throat. Those few examples have other flowers in the same original photograph in the iNat observation that do not have a similar red line. Click on the pictures to go to the original iNat observation. | |||
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| Fig. 5. Variation in the flowers of C. heterophylla. The photographs are arranged in order of the color of the lower lobes, from light pink to pink-purple to dark pink-purple to blue-purple. The photos come from all iNat observations that I examined which had a good frontal view of the flowers, were in focus, and had flowers that were comparable in size to the others in this Figure.
Note also the variation in the color of the upper lobes, from nearly pure white, to pinkish-white with blotches at the tips, to pink-purple, to bluish, which roughly correlates with the color of the lower lobes. The dark throat is easy to see in most of the pix. The red line at the base of the squarish blotch area is usually visible as well. Click on the pictures to go to the original iNat observation. | |||
Introduction
To be added.
Distinguishing Characteristics
See Figures.
Geographic Distribution
Fig. 6 shows the geographic distribution of the two species from vouchers from San Diego County at the San Diego Natural History Museum. Vouchers from elsewhere are generally not as accurately determined, showing, for example, voucher determinations of "C. concolor" in areas where only C. heterophylla is present.
Fig. 6. Geographic distribution of Collinsia concolor and C. heterophylla from the San Diego County Plant Atlas page, retrieved on 27 May 2024.
Fig. 7 shows a preliminary geographic map of the two species from vouchers from San Diego County at the San Diego Natural History Museum, augmented with my determinations of iNat observations for the area east of the line from Fig. 3. I'm still in the process of reviewing observations, but by and large, it looks like the characteristics from Figs. 1 and 2 do a very good job of correctly determining photographs, and they appear to work as well, or better, than voucher determinations.
As of 8 June 2024, I've examined 127 iNat observations determined as "C. heterophylla" for the area east of the line in Fig. 3. I verified that 76 of those observations were indeed C. heterophylla, but 51 of those observations were actually of C. concolor. The plot in Fig. 7 shows those 127 iNat observations, along with 19 C. concolor iNat observations I verified in the work reported in Figs. 4 and 5. I haven't examined any of the 313 other iNat observations in that area determined as C. concolor.
I discarded iNat observations with a position uncertainty of more than 0.5 km.
To finish my iNat review, there are 55 additional iNat observations of "C. heterophylla" east of the line that I have yet to review, as well as the 313 additional iNat observations of "C. concolor".
Update 16 June 2024: I've finished reviewing the iNat obs of "C. heterophylla" east of the line, and reviewed all iNat obs of "C. concolor", so the map is now complete. The text has not been updated, but Fig. 7 has.
Fig. 7. Geographic distribution of Collinsia concolor and C. heterophylla from San Diego Natural History Museum determined vouchers, retrieved on 27 May 2024, along with my determinations of iNat observations for the area east of the line from Fig. 3 as of 16 June 2024. The plot has been distorted from geographic correctness in order to show the individual points better in areas where they overlap.
The iNat determinations made by me are in very good general agreement with voucher determinations from San Diego Natural History Museum (SD). The northeast, east, and southeastern portion of the county have only C. concolor except for a single SD voucher in the northeast portion that appears to be incorrectly determined or incorrectly georeferenced.
The central part of this map east of the line is also in good general agreement, with C. heterophylla the dominant species.
There are five areas where the two species come into contact. From north to south, they are:
- Palomar Mountain at (-116.91, 33.34), which is almost entirely C. concolor at the top and north side, except for a few C. heterophylla occurrences at Boucher Hill, and on its southern side in Pauma Valley.
- Wynola area near (-116.65, 33.1).
- Julian area near (-116.6, 33.08), where both species were found at the same location, and previously placed in a single observation.
- Cuyamaca Rancho State Park area at (-116.57, 32.9), where the entire area is C. concolor except for the southeastern edge.
- Pine Valley west of Corte Madera Mtn, north of Barrett Lake, south of Japutul Valley, and east of Lawson Valley.