Unveiling the ecological dominance of button mangrove (Conocarpus erectus L.) through microstructural and functional traits modifications across heterogenic environmental conditions

Abstract

Background: The button mangrove (Conocarpus erectus L.) is regarded as a peripheral species within mangrove communities. This particular species has the ability to thrive in regions that are arid or semiarid, where there is limited availability of nutrients. This study provides evidence of the ecological dominance of Conocarpus erectus across various habitats, highlighting its adaptability and success throughout the country of Pakistan. We collected twelve populations from four distinct ecological regions, including artificial forest plantations, agricultural fields, roadsides, and wastelands, offering a comprehensive assessment of C. erectus adaptability across diverse environmental contexts.

Results: Forest plantation populations exhibited impressive shoot growth and moderate root lengths, with plants generally tall and well-weighted. Physiologically, they had moderate chlorophyll content and low carotenoid levels, with a balanced chlorophyll a/b ratio, indicating stable photosynthetic activity. Anatomically, these populations had thicker epidermal and cortical root layers but smaller vascular bundles and phloem regions. Stem and leaf structures were generally moderate in size, with thicker midribs and cortical layers in the leaves. Agricultural field populations showed robust shoot and root systems with balanced fresh and dry biomass. They exhibited high chlorophyll and carotenoid levels, indicating strong photosynthetic capacity. Root and stem anatomy revealed larger root areas, thicker cortex, and wide vascular bundles, reflecting enhanced structural development. Leaves from these populations had moderate midrib and cortical thickness, with larger stomatal areas, promoting efficient gas exchange. Roadside populations displayed deeper roots and reduced biomass production. These populations adapted to environmental stress through leaf expansion, with high leaf numbers and areas. Physiologically, populations had high chlorophyll content, with a high chlorophyll a/b ratio. Root and stem anatomy showed compact structures with smaller vascular bundles, indicating adaptation to harsher conditions. Leaf anatomy was moderate, with smaller vascular bundles and reduced water transport capacity. Wasteland populations exhibited poor growth and high shoot biomass despite small leaves. Physiologically, these populations had the highest total soluble protein and proline contents, reflecting stress adaptation. Anatomically, root and stem structures were variable, with some populations showing reduced cortical cell areas and smaller vascular bundles, indicating limited resource transport. Leaf structures had thicker lamina, thinner epidermal layers, and lower stomatal densities, reflecting adaptation to nutrient-poor soils.

Conclusion: This study reveals the adaptability and thriving potential of Conocarpus erectus across varied habitats, providing key insights into its resilience and survival strategies. Understanding these adaptive traits can support habitat restoration, conservation planning, and improve species management in diverse environmental conditions, especially in response to climate change and habitat degradation.

Keywords: Adaptive strategies; Button Mangrove; Osmoregulation; Succulence; Xeromorphy.

Fig. 1

Representing the Punjab map containing collection sites and pectoral view of Conocarpus erectus collected from diverse habitats. C1-Chak 1; C4-Chak 4; C9-Chak 9; BAS- Basti Sheikh; C2-Chak 2p; DAS- Dari Sangi; DBS- Dera Bibi Sugra; DHS- Dhoop Sari; FLC- Flood Colony; HOP- Hospital 1p; KNK- Khanpur Nawan Kot; MOT- Model Town

Fig. 2

Root transvers sections of Conocarpus erectus populations collected from the Punjab province (Mx = 40X; n = 6). Description: 1) forest plantation; a Chak 1-thicker epidermis, large lysigenous cavities, reduced metaxylem vessels and pith region, b Chak 4-thicker epidermis, partially crushed root region, very reduced metaxylem vessels, c Chak 96-reduced root area and partially crushed from one side, enlarge metaxylem vessels. 2) agriculture fields; d Basti Sheikh-rounded and thicker root section, large metaxylem vessels and pith region, e Chak 2P-thicker epidermis, partially crushed cortical region, reduced metaxylem vessels, f Dari Sanjhi-enlarge root cellular area, compact cortical region, very reduced xylem vessels.3) roadsides; g Dera Bibi Sughra-partially crushed root cortical region, thick endodermis, enlarge pith region and xylem vessels, h Dhoop Sari-very reduced root cellular area and little crushed, greatly reduced metaxylem vessels and pith area, i Flood colony-thick epidermis, large cortical region, xylem vessels large and sparsely arranged.4) wastelands; j Hospital-greatly reduced root region, large laygenous cavities, reduced pith and metxylem area, k Khanpur Nawan kot-thick root and partially crushed, large metaxylem vessels and pith region, l Model Town-enlarge root cellular area with large lysigenous cavities, enlarge metaxylem vessels and pith region

Fig. 3

Stem transvers sections of Conocarpus erectus populations collected from the Punjab province (Mx = 40X; n = 6). Description: 1) forest plantation; a Chak 1-triangular stem, thick epidermis and cortical region, prominent pith region, b Chak 4-reduced stem area and cortical region, enhanced pith thickness and metaxylem area, c Chak 96-thick stem area, reduced cortical region, enlarged pith region and its cell area. 2) agriculture fields; d Basti Sheikh-thick and rounded stem, enlarged pith area, reduced xylem vessels, e Chak 2P-enlarged stem cellular area, metaxylem vessels and pith region, f Dari Sanjhi-triangular stem, thick cortical region and pith area, enlarged xylem vessels. 3) roadsides; g Dera Bibi Sughra-extraordinary thick stem cellular area and epidermis, reduced xylem vessels, h Dhoop Sari-triangular stem, enlarged metaxylem vessels and pith region, i Flood colony-reduced stem area, cortical region and pith cellular area, enlarged xylem vessels.4) wasteland; j Hospital-extraordinary thick stem area, enlarge xylem vessels and pith cells area, k Khanpur Nawan kot-thick stem with reduced cortical region and metaxylem area, enlarged pith, l Model Town-enlarged stem area with large lysigenous cavities, xylem vessels and pith region

Fig. 4

Leaf transvers sections of Conocarpus erectus populations collected from the Punjab province (Mx = 40X; n = 6). Description: 1) forest planation; a Chak 1- thick leaf with thick lamina and midrib, enlarged cortical parenchyma, reduced vascular bundles, b Chak 4-reduced leaf thickness, cortical parenchyma cells large, enlarge vascular bundles, c Chak 96-thick leaf with reduced lamina, enlarge cortical parenchyma and vascular region. 2) agriculture fileds; d Basti Sheikh-thick leaf with reduced lamina, large cortical parenchyma, narrower vascular bundles, e Chak 2P-thick leaf with reduced lamina, enlarged cortical region and vascular bundles area, f Dari Sanjhi-thick midrib with reduced lamina having large cortical region, greatly enlarged vascular bundles.3) roadsides; g Dera Bibi Sughra-extraordinary thick leaves, enlarged vascular bundles, reduced lamina thickness, h Dhoop Sari-elliptical leaves with reduced lamina, enlarged cortical region and vascular bundles area, i Flood colony-very thick leaf with reduced lamina, sparse hairiness and large cortical region.4) wasteland; j Hospital-greatly thicker leaves with reduced lamina, enlarge cortical parenchyma and vascular region, k Khanpur Nawan kot-thick leaf with narrow lamina, enlarge cortical region and vascular bundles area, l Model Town-thick leaf with narrow lamina and partially crushed cortical region, enlarged vascular region

Fig. 5

Epidermal transvers sections of Conocarpus erectus populations collected from the Punjab province (Mx = 40X; n = 6). Description: 1) forest plantation; a Chak 1- stomata small, narrower and deeply seated in epidermis, b Chak 4-small, narrower and sparsely arranged stomata, c Chak 96-stomata large and numerous with sparse alignment. 2) agriculture field; d Basti Sheikh-stomata few and small with sparse arrangement, e Chak 2P-stomata few and small with irregular alignment, f Dari Sanjhi-very large and numerous with irregular alignment. 3) roadsides; g Dera Bibi Sughra-very lare stomata with irregular arrangement, h Dhoop Sari-stomata very small and deeply seated in epidermis, i Flood colony-few and large stomata with irregular arrangement. 4)wasteland; j Hospital-stomata large and numerous with sparse alignment, k Khanpur Nawan kot-very few and small stomata with irregular arrangement, l Model Town-very enlarge stomata with regular alignment

Fig. 6

Principle component analysis (PCA) showing influence of soil physicochemical characteristics on A growth attributes and physiological attributes, B root anatomy, C stem anatomy and D leaf anatomical features of Conocarpus erectus from Punjab province

Fig. 7

Clustered heatmaps showing association of soil physicochemical features with A morphology and physiology, B root anatomy, C stem anatomy and D leaf anatomical characteristics of Conocarpus erectus from Punjab province

Fig. 8

Adaptive component of Conocarpus erectus populations in response to diverse habitats of Punjab, Pakistan